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>
PH0T0GE4PHED SPECTEA
LO:7DON : PEIXTED DT
aPOTTISWOODK AKD 00., NBW-8TnBKT SQUABB
AXU PARLIAMENT STQEET
PHOTOGRAPHED SPECTRA
ONE HUNDRED AND THIRTY-SIX PHOTOGRAPHS OF
METALLIC, GASEOUS, AND OTHER SPECTRA
PRINTED BY THE PERMANENT
AUTOTYPE PROCESS
WITH
INTRODUCTION, DESCBIPTION OF PLATHJSy AND INDEX
AND WITH
AN EXTRA PLATE OF THE SOLAR SPECTRUM
(SHOWING BRIGHT LINES) COMPARED WITH THE AIR SPECTRUM
BY
J. EAND CAPRON, F.ll.A.S.
^ q'
o,
V .
H\
LONDON
E. & F. N. SPON, 46 CHARING CEOSS
NEW YOKK: 446 BllOOME STKEET
1877
PHOTOGEAPHED SPECTEA.
■•o«-
INTRODUCTION.
During the course of the last and the preceding
winters, I was led, in connection with an investigation
bearing on the Spectrum of the Aurora, to take photo-
graphs of certain of the metallic and gaseous Spectra
with a spectroscope of moderate dispersion. After a
time this work gradually extended itself, and ultimately
a very considerable collection of such photographic
plates was obtained. In these labours I was very
efficiently assisted by Mr. G. H. Murray of the Surrey
Photographic Company (who superintended the photo-
graphic department), and by Mr. E. Dowlen of Guild-
ford, to whom I am much indebted for notes and general
assistance. The photographic impressions comprised
all that could be obtained of the spectrum in each case,
ranging from about b to beyond H^ H^ in the violet.
It was soon apparent from an examination of the plates
obtained, —
1. That considerably more of the spectrum was
obtained in the direction of the violet end than
is ordinarily delineated in the published works
on Spectra.
B
2 PIIOTOGRAPFIED SPECTRA.
2. That, notwithstanding the moderate dispersion
and the limited extent of the spectrum obtained
(for want of the red end), each individual
photograph had, without actual measurement
of its principal lines, a separate and distinct
character, easily recognised when once seen,
and distinguishing it from all others. This
peculiarity we think will be borne out by an
examination of the Plates produced, and we
ourselves had several practical instances of its
application in our process of taking the photo-
graphs.
Under these circumstances we considered we might,
with probable advantage to others engaged in spectro-
scopic research, reproduce a series of our results as
forming at once a handy book of reference to spectra
in general, and as also illustrating in each particular
case the peculiar features of the spectrum photo-
graphed.
The spectroscope employed (for the metals) was
constructed by Mr. John Browning some years ago
specially for Auroral observations, and is of the direct
vision form.
The prism is an inch aperture compound (5) one,
dividing very easily the D lines with a low eyepiece,
a similar second prism can be slipped in for use if
desired. The collimator carries an 1^ achromatic lens of
6 inches focus. The ordinary observing telescope and
eyepiece were removed, and an 1^ achromatic projecting
lens of 9 inches focus was substituted for them. The
INTRODUCTION. 3
short tube carrying the last-mentioned lens was con-
nected by a black velvet bag, with an ordinary square
camera for plates 4 J -f 3 J, and the images were taken
upon collodion wet plates. (See Frontispiece for
arrangement of apparatus).
The metallic spectra were obtained of tjvo sorts :
1. By the spark.
2. By the electric arc.
The metals employed mostly formed part of a
German cabinet which came into our hands with a
good character.
For obtaining the spark spectra, the apparatus con-
sisted of a large EhumkorfFcoil, giving, with four double
plate half-gallon bichromates, a thick strong spark
about 2 inches long. In the circuit was introduced a
condenser, composed of 4 glass plates, each containing
50 square inches of coating. By this condenser the
spark was reduced to one from ^ to ^ an inch long,
and of considerable brilliancy. The time of exposure
in the case of the spark spectra varied very con-
siderably, averaging perhaps 15 minutes.
For the arc spectra 40 pint Grove cells (except in
one or two instances when 30* only were used) were
employed, and with these the arc was steady and of
sufficient length. In all cases the slit was placed
vertically ; and in our printed Plates we have followed
the usual practice of spectroscopists, in keeping the red
end of the spectrum to the left hand. Care was taken
to have the carbon points and cups well cleansed, and
by trial plates, taken from time to time, it was seen
B 2
4 PHOTOGRAPHED SPECTRA.
that they contained no impurities affecting the spec*
trum.
For the spark, wires or points of metal, held by
miniature steel pincers, were used.
In the case of the arc, sometimes fragments of the
metals, sonaetimes the metal in powder, and in a few
instances solid metal electrodes were employed. The
time of exposure in the case of the arc ranged from
three to five minutes, according to the intensity of the
stream of hght. The length and brilliancy of the arc
were found to alter much according to the nature of
the metal placed in the cup. The spark also varied
considerably in length and intensity according to the
electrodes. In the spark spectra, the air spectrum is,
with a few exceptions, seen in company with the metal
lines, the latter being, however, easily distinguished
from the former by their passing only partly across the
spectrum, while the air lines cross it entirely.
In the arc spectra some carbon lines of constant place
seem the only foreign introductions into the system of
metallic lines. These carbon or, as we called them,
' point ' lines, are found useful in placing and compar-
ing the several spectra when obtained. The images as
thrown on the camera plate were rather more than
two inches long ; and these were subsequently enlarged
exactly once. The lines required very careftil focussing,
the slit being in most cases fine, so that where lines
are found thickened it is in general due to their
character. To supply the want of an approximate
scale, and also to indicate the part of the spectrum.
INTRODUCTION. 5
photographed, I prepared a diagram in which two
spectra of the metal manganese were respectively com-
pared, and a scale obtained by direct interpolation.
The upper horizontal spectrum was a photograph ob-
tained from manganese in a rather weak arc (30 cells).
The vertical spectrum was an enlarged (by photo-
graphy) copy of Monsieur Lecoq de Boisbaudran's
normal spectrum of chloride of manganese (' Spectres
Lumineux, Atlas,' Plate xvii). The curve obtained was
regular, and a subsequent comparison of the result with
the solar spectrum of the same instrument (Plate xxi)
is satisfactory. The scale in most cases fairly coincides
for the principal lines with Monsieur de Boisbaudran's
spectra, but instances will be found where the photo-
graphed spectral images are not in themselves ab-
solutely uniform in exact length and position of
fiduciary lines. The causes of this are not yet fully
worked out, but we believe the result to be due to a
difference in certain cases in distance of the discharge
from the slit. To the Description of the Plates are
added some notes by way of information as to the
behaviour of the metals and on other points.
The wave lengths of lines (where given) are
taken partly from M. Lecoq de Boisbaudran's work,
'Spectres Lumineux,' and partly from Dr. Watts'
' Index of Spectra.' The photographs were all taken
on separate plates, and have been very well re-
produced and printed in permanent pigments by the
Autotype Company, in compared sets of four. They
are for convenience arranged in alphabetic order,
6 PHOTOGRAPHED SPECTRA.
the upper metals in the plates being selected for
arrangement where electrodes of different metals were
employed. Spark and arc spectra of the same metal
are in many cases compared. A few of the metals
and metalloids are wanting, mainly from the diflSculty
of obtaining with our apparatus, spectra bright and
permancDt enough to impress images on the photo-
graphic plates. The arc photographs might with
advantage bear considerably greater enlargement, but it
was thought convenient to keep them, for the purpose
of comparison, of the same size as the spark spectra.
Some of the metals do not show their full set of lines,
probably for want of more coil power; but there
were considerations why a moderate spark was
originally selected, and the spectra were subsequently
kept uniform in this respect.
When rough lumps of metal were used for points
the spark was generally winged (especially when the
batteries were fresh), and played about over the surface
of the metal. The wings of the spark were tinged
with green in the case of silver and copper, with red in
that of iron, white or bluish white with magnesium.
Titanium ore gave occasional flashes of red (probably
from the iron clips), sodium gave a bright yellow flame,
l^he cups used with the spark apparatus were of
aluminium, except where glass is mentioned.
Width of slit averaged -003 inch, except in one or
two instances which are especially mentioned.
When diflferent metals were used as terminals, the
current was generally reversed in the middle of the
exposure.
INTRODUCTION. 7
The carbon terminals used in the arc were cut
from ordinary gas carbons, 3 centimetres long and 6
millimetres square. Those for the negative pole had
one end filed to a point. Those for the positive pole
were hollowed out at the end with a drill so as to form
a cup. To get rid of impurities (of which iron formed
the principal part), the carbons were soaked alternately
in acids and water : First, they were soaked in
diluted sulphuric acid, 2 parts water, 1 acid, then
soaked in water. Secondly, in dilute nitric acid, equal
volumes of acid and water. Thirdly, in hydrochloric
acid, half volume of water. The acids and water were
changed several times during the soaking. Last of all,
the carbons were soaked in water alone, which was
repeatedly changed imtil all the acid was washed out.
They were then slowly dried in an evaporating dish over
the flame of a Bunsen burner. The acids were all pure,
and the water distilled. The whole process occupied
from one to two weeks, according to the density of
the carbons, some being more porous than others.
When metals in powder were used in the arc,
small beads of the metal were usually scattered over
the inner surface of the cup, the main portion of the
metal remaining at the bottom.
All the metals of the iron group gave out sparks,
viz., manganese, iron, cobalt, nickel, chromium, and
uranium. Silver gave a melted bead, which revolved
in the carbon cup without actual contact with it. The
width of the slit was generally '001 inch, distance of arc
from slit 1^ inch, but from the flame playing round
8 PHOTOGRAPHED SPECTRA.
the point and cup, this distance was subject to varia-
tion. The adjustment for distance of arc discharge
was by rack work worked by hand. The upper
carbon was fixed in a ball-and-socket joint so as to
adjust easily over any part of the cup.
A fresh pair of carbons was used for each metal.
Much trouble was found in keeping the slit, and the slit
plate clear from metallic beads and other impurities.
It would be a great advantage for fiiture similar work
to have the whole slit plate gilded and the slit jaws
formed of obsidian, platinum, or gold.
The gas spectra are represented in the last fifteen
Plates ; and for the purpose of obtaining these it was
found necessary to resort to a difierent form of instru-
ment to that employed for the spark and arc spectra.
An attempt was at first made to take all the spectra
with the same instrument, but it was soon found that less
dispersion and a brighter image would be required to
give any useful results with the gases, and one only of the
series (viz., spark in coal gas), was taken with the same
instrument as the metals.
Three forms of instrument were then arranged and
used for gaseous spectra : —
A — A compound (5) direct vision prism on stand
similar to that used for the spark and arc spectra, but the
colhmating and projecting lenses of the spectroscope
were replaced by two camera lenses of somewhat larger
diameter, and each of 4| inches focus. The image was
fairly bright, but not very sharp, as the slit could not be
made very fine without loss of light.
INTRODUCTION. 9
B — A table spectroscope constructed for me by Mr.
Browning with two quartz (inch) prisms of 60° angle,
the coUimating and projecting lenses being also of
quartz 1^ inch in diameter, and of 6 inches focus.
The images with this instrument were brighter than
those with the last instrument (A), were of fair defini-
tion, and penetrated more into the violet.
C — This last instrument was also a table spectro-
scope, made for me by Mr. Browning, with a view to
the photographing faint spectra.
The prism is a large compound (3) one, IJ inch
high, 2 inches across' and 4f inches in its longest base.
The colhmating and projecting lenses are from a fine
field glass 2 inches in diameter and of 7 inches focus.
Our experience led us to conclude that considerable
aperture of prism and of lens was absolutely essential
for the production of bright and sharp images. This
Mr. Eutherford had previously demonstrated in
America. The images from our instruments of small
aperture bore no comparison whatever with those
afforded by the larger instrument now describing.
With the latter the images were very bright, and the
lines wonderfully well defined and separated for so
small an amount of dispersion. The impressions are
quite small on the photographic plate (less than half an
inch in length), but so sharp that they would bear
enlarging nine or ten times • without material loss of
definition.
In the Plates of the gases the images obtained from
spectroscope A are enlarged twice, those from spectro-
10 PHOTOQRArHED SPECTRA.
scope B, (quartz), are also enlarged twice. Those from
spectroscope C are enlarged rather more than five times.
The spectra from A and C spectroscopes are en-
larged so as nearly to correspond in dispersion and in
actual dimension. Those from the spectroscope B
(quartz) are on a smaller scale altogether, and are
mainly used where comparison of spectra is desired.
The spectra of the gases (except in one or two cases)
were obtained from the exhausted tubes of the Geissler
form commonly used in spectroscopy, some of foreign,
some of home preparation. The latter were found best
adapted for our work, being larger in the bore and bulbs,
and bearing stronger currents without injury. For
working the tubes, two different coils were used. The
smaller one was a half-inch coil such as is generally
sold for the purpose of hghting up tubes in spectral
work, and was excited by a quart bichromate. The
larger coil was that employed for the spark spectra
before described ; it was worked by two half-gallon
bichromates only. This instrument has a large heavy
break of the common form, but with screw adjustments
enabling the rate of vibration to be easily controlled
during work ; a very steady current was obtained by
this means. The smaller coil was used for single tubes ;
and such as would hght up easily. The larger coil
was used in cases where two tubes were employed, for
line spectra and for tubes which required much lighting
up. When line spectra were wanted, the condenser
before mentioned with two plates taken out, or a
small Leyden jar was introduced into the circuit, the
INTRODUCTION. 11
rate of discharge being regulated by the distance be-
tween two platinum points on a stand, which formed part
of the connections. When the large coil was employed
for a single tube, a second larger tube was usually
introduced into the circuit to diminish the heating
effect of the current. The time of exposure for the
tubes was about twenty minutes with spectroscopes A
and B, and from tw^elve to fifteen minutes with spectro-
scope C. The tubes which lighted up most easily and
were not damaged by the continuous current, were
nitrogen, carbonic acid, coal gas, cyanogen, hydrogen,
oxygen, silicic fluoride, and olefiant gas. All these
photographed more or less easily. The tubes which
gave us more trouble were bromine, iodine, chlorine,
ether vapour, turpentine vapour, sulphur, and tin
chloride : bromine and chlorine we failed to get
photographs of. These tubes broke down before they
had been lighted a sufficient length of time to
impress an image. Iodine vapour tube failed also in
this respect ; but we succeeded in photographing
(though not well) the spectrum of the spark in a bulb
filled with iodine vapourised. The tin chloride tube
also soon broke down, and we obtained only one plate
from it. Further particulars of the behaviour of the
tubes will be found in the Description of the Plates. In
all cases a photograph was first tried of the single tube
as filling the whole length of the slit, this last being
intentionally as long as the instrument would bear.
When the slit was reduced in length, whether by the
comparison prism being used or in any other manner, a
12 PHOTOGRAPHED SPECTRA.
manifest falling off of the photographic effect in point of
brightness of image was apparent. It was only with
the instrument C that we could use quite a fine sht.
In the course of our experiments we tried the effect of
an electro-magnet upon some of the tubes. Our
magnet was one of Ladd's, of the size used for dia-
magnetic experiments, with arms 10^ inches long and
poles 2 inches across and with large movable coils of
insulated copper wire. It was excited by the four
half-gaUon bichromates before referred to. Probably
with more battery power we should have obtained
changes in the spectra themselves in accordance with
the experiments of Monsieur J. Chautard. It was, also,
unfortunate that chlorine, bromine, iodine, sulphur,
and tin chloride, from which he obtained his best
results, were just the tubes which gave us the most
trouble in a photographic way. The magnet was fitted
with conically pointed armatures ; between the points
of which we placed the capillary part of our tubes.
In this way danger arose to the tubes, as the armatures
when the current was passing would draw together
with sufficient force to crush the glass. We secured
the armatures in their places by turning out circular
edges on their bases, and so arranged that the blunted
points would just take the thickness of the tube between
them. Our experiments were mainly without much in
the way of positive 'results. The stream of light was
in most cases narrowed, and appeared to experience a
certain amount of resistance in its passage (in the case
of siUcic fluoride a sort of sharp whistling sound was
INTRODUCTION. 1 3
heard when the magnet was excited), but we did not
detect any palpable change in or addition to the
spectral lines. Only in the case of nitrogen did we get
any very marked effects, and this was somewhat
peculiar as M. Chautard classes this gas amongst those
upon which ' the influence of the magnet is hardly per-
ceptible,' (' Phil. Mag.' S. 4, vol. 50, p. 79). A Geissler
nitrogen tube having been placed between the poles of
the magnet, it was lighted up by the small coil. The
stream of light was steady and brilliant, and (except at
the violet pole) of the rosy colour peculiar to a nitrogen
vacuum tube. On the excitation of the electro-magnet
the discharge at once appeared diminished in volume,
with an apparent increase in impetuosity ; and not only
the capillary part but in a less degree the bulbs also of
the tube changed from a rosy to a well-marked violet
tint. We several times connected and disconnected the
magnet with its batteries, but always with the same
result.
This effect of shifting tint was very striking, and
assuming the Aurora to be wholly or in part of electric
origin, is strongly suggestive of a reason for the varying
tints of the streamers which are frequently observed.
Of the spectrum of the capillary part of this tube we
took two plates, taking care that all things should be
as equal as possible, the apparatus undisturbed, and the
time of exposure exactly the same. One plate was
taken while the tube was in its normal condition, the
other while the tube was influenced by the magnet.
The plate H- magnet will be seen to penetrate more into
14 PHOTOGRAPHED SPECTRA.
the violet, though the character of the spectrum itself
does not appear altered. An eye- view of the tube
with the spectroscope also showed us no definite
variation in the spectrum, nor could we trace
that the violet pole spectrum extended itself under
the altered condition of the tube as to tint. We
tried also a large bulb Plucker tube in which the aura
from the violet pole was condensed into a bright arc
under the influence of the magnet. No change of the
violet tint was here remai-ked, but only a brightening of
the light consequent upon its condensation. Plates in
this case also gave slightly more of result in the violet.
In the case of silicic fluoride the stream of light was
diminished in volume, and the plate from the tube
without the magnet is decidedly the brightest. In
other respects the plates are alike.
Our experiments of course do not conflict as com-
pared with M. Chautard's, as the battery employed on
our magnet was far inferior in power to his (he used
from twelve to fifteen large Bunsen elements), but our
experience with regard to the nitrogen lube seemed
worth recording.
Li taking our spectra, and specially the gases with
spectroscope C, we had to exercise great care in the
focussing on the plate. For this purpose the finest
ground glass for the plate and a strong magnifier to
view the image were employed. The rough adjust-
ment was first of all obtained by moving the camera
on its heavy base, and the fine adjustment was then
completed by means of a screw motion in the same
INTRODUCTION. 15
base. It must not be supposed that the Plates printed
were all we obtained, probably not more than one in
three which were taken were selected for enlargement.
In nearly all cases we took two plates of the same
spectrum, although the first might be good ; and fre-
quently from the heat of the room and other causes
plates good as to spectral image were imperfect as
photographs. In fact anyone wishing to try the same
work on the same or a larger scale must expect partial
failure and disappointment, until experience has been
gained in it. Kennett's dry plates would have some
advantages over the wet plates we employed, but they
would also be subject to the drawback of taking longer
to develop, so that except with the loss of much time,
one could not, as we did, develop and examine the
plates obtained at once and before the points and other
apparatus were displaced for a next experiment. Our
results of course are not intended to be placed by the
side of photographs of spectra of larger dispersion taken
for comparison of the metals, study of the solar spectrum,
etc., but they may perhaps prove useful to amateurs
and others, working with spectroscopes of small dis-
persion, for comparison of spectra in their general aspect,
and for study of the points and peculiarities attaching
to most spectra, which are generally brought out
in our prints. To those v/ho have the time and
opportunity there seems much to invite a taking up of
the whole subject on a more extended scale and with
more complete apparatus.
Absolute truth is everything in spectroscopic work,
16 PHOTOGRAPHED SPECTRA.
and the very best drafitsman working with the most
perfect micrometer cannot, even at the expense of a
vast amount of labour, equal in accuracy a good photo-
graph of a set of spectral lines. Photographs, too, have
the great advantage that they may be enlarged and
tested at leisure ; and if several plates of the same
spectrum are taken and subsequently compared, the
investigation for certainty of result is only a matter of
time and trouble.
I ought to mention that we tried in the case of the
spark spectra (but without advantage) tinted collodion,
with a view to work more towards the red end. The
tinting substances used were Magenta, Judson's Violet,
Annatto, Saffron, Turmeric, and Chlorophyll. Dr.
Huggins' success in stellar photography with Iceland
spar prisms promises a considerable extension of the
spectrum in the ultra violet direction, and some recent
investigations of Captain Abney and others work in the
direction of the yellow and red regions, so that there
is good hope of obtaining at no distant date a wide
range of photographs including aU of the visible
spectrum, and more. Of what assistance such faithful
light pictures would prove to science, I need not here
point out, except as an apology for our present attempt
to popularise a subject hitherto somewhat of a sealed
book confined to the laboratories of workers in special
research.
17
DESCRIPTION OF THE PLATES.
PLATE I.
First Print. The Scale, — The scale has been already
referred to in the Introduction. The photographs of
the metals are so masked that in general when the
scale is applied to them, it falls in its right place or
very nearly so. To enable, however, the scale to be
applied with greater exactness two fiduciary marks or
points are indicated upon it, the one a bright line
marked ' spark ' situated between h and F, the other a
set of seven carbon or point lines between G and h
marked ' arc' For the spark spectra the scale is ad-
justed by applying the bright line marked ' spark,' to
the bright line which appears prominently at the left
hand of each spark spectrum. To adjust the scale for
the arc spectra the set of lines marked ' arc,' are to be
applied to the corresponding set of lines which are to
be distinguished in most of the arc spectra towards the
violet end, and which are the principal ones derived
from the points and are considered as carbon or carbon
compounds. Two prints are given of the scale, one on
Plate I., and the other on Plate XXI., so that if direct
c
18 PHOTOGRAPHED SPECTRA.
application and comparison are desired one of them may
be cut out and used for the purpose.
Second Spectrum. Air with wide slit.
Third Spectrum. Air with fine slit.
These two spectra may be described at the same
time. They differ only in length of the spark (which
was taken between platinum points) and width of the
slit.
The lines comprised in them may be traced more or
less throughout all the spark spectra, and form useful
indices for position of metal lines.
Lecoq de Boisbaudran gives [Spectres Lumineux,
Plate II., Etincelle longue], a spectrum comprising
hues (with others) 5003, 4805, 4706, 4648, 4633,
4449, 4434, 4347, and a band at 4240. This spectrum
resembles generally our present spectrum, though it
fails to agree in some respects, probably from the in-
troduction of the condenser in our case. Our spectrum
is for the stronger lines, identical with that of the hne
spectrum of the capillary part of a nitrogen tube. {See
Plate XXV. Fourth Spectrum).
Fourth Spectrum. Arsenic Spark. — Small rough
lumps of the metal placed in the clips. Spark white,
and striking with ease across a considerable distance.
Slight fumes of oxide at first, exposed twenty minutes.
Two plates taken which were strictly identical, each
showing the fiizzy bands on the margin of spectrum
midway between F and G from about 4575 to 4475,
and the lines in the bright part of the spectrum about
4400, 4355, and 4310. Dr. Watts, in his ' Index of
DESCRIPTION OF PLATES. 19
Spectra,' does not continue the spectrum of Arsenic
beyond 5324 towards the violet ; but faint lines are,
given on Huggins' authority, at 4551, 4537, 4497, a
stronger one at 4464 and faint ones at 4369 and 4335.
PLATE n.
First Spectrum. Aluminium Spark. — Pieces of the
metal in clips. Spark moderate in length, ten minutes
exposure ; also tried with condensing lens in front of
slit. Sht rather wide.
Second Spectrum. Aluminium Arc, — Piece of
metal cut from small bar, in carbon cup. Arc short,
slit fine.
Principal line in the spark spectrum at about 4500.
This is represented in the arc by the edge of one of
three sets of shaded bands.
The two very conspicuous lines in the arc, between
ff and H'^, are only represented by one near H^ in the
spark. The edges towards the violet of the shaded
bands in the arc are given by Lecoq de Boisbaudran
[Plate XV., Aluminium metallique], at 4845, 4652, and
4478. And the intense lines between H^ and H^ at
3962 and 3943, (H^ is given in Watts' ' Index ' at 3968
and IF at 3933).
Third Spectrum. Antimony Spark. — ^Eough ] umps
of metal in clips. Spark bright and broad.
Fourth Spectrum. Antimony Arc. — Small pieces
of metal in carbon cup, arc of moderate length, much
oxide formed.
c 2
20 PHOTOGRAPHED SPECTRA.
The spark spectrum is peculiar owing to the stream
of light running along each margin of the spectrum,
apparently thickening at each extremity, not only the
metal, but also the air lines. Some of the air lines
however escape ; proving that the appearance has not
to do with the slit, but must be caused by metallic
vapour hanging about each pole. (See also Lead and
Antimony, Plate X., Fourth Spectrum.)
The arc spectrum gives little beyond the point
lines. We took several plates, but always with the
same result in this respect. The lines given by Lecoq
de Boisbaudran, [Plate XXTTT., Proto-chloriu-e d'An-
timoine], are 5037, 4947, 4877, 4787, .4711, and
Dr. Watts continues with 4693, 4588, 4349, and 4264.
(See Lead and Antimony before referred to, where the
lines are somewhat more distinct.)
PLATE m.
First Spectrum. Bismuth Spark. — Pieces of the
metal in each clip, exposed ten minutes, spark bright.
Second Spectrum. Bismuth and Nickel Spark. —
Pieces of metal in clips, exposed ten minutes, current
reversed at half. Note extension of metal lines in the
middle of the spectrum, in consequence of breaking
away of the point.
Third Spectrum. Bismuth and Tellurium Spark
Pieces of metal in clips, exposure ten minutes, current
reversed at half. Tellurium partly fused, spark struck
over Tellurium to the clip, (notice some iron lines from
DESCRIPTION OF PLATES. 21
the clip projecting beyond centre of the spectrum at
Tellurium pole).
Fourth Spectrum. Bismuth Arc, — Piece of metal
in carbon cup, arc moderate.
The spectrum of bismuth with spark obtains easily,
and the lines are well marked, those in the centre of
the spectrum widening out considerably and showing
in strong contrast to the air lines.
Lecoq de Boisbaudran gives (Plate XXII., Chlorure
de Bismuth), 5209, 5144, 5123, 5049, (4965, 4882),
4724 (characteristic), 4303, 4259, 4118 (characteristic).
Most of these lines appear in our spark spectrum,
with others in addition.
The principal lines in our arc spectrum are about
4750 (very bright), and 4120 (probably Boisdaudran's
4118). The vivid lines in the bright part of the spark
spectrum do not appear in the arc.
As to the second spectrum (Bismuth and Mckel),
Lecoq de Boisbaudran gives [Plate XIX., Chlorure de
Nickel], lines at 4873, 4867, 4856, 4832, 4808, 4788,
4762, 4755, 4732, with principal ones at 4715 and
4401. Our spectrum extends more into the violet, and
shows a very bright line near H^
The Tellurium spectrum will be referred to in its
order further on,
PLATE 17.
First Spectrum. Barium Spark, — Small pieces of
metal in the clips which fused away rapidly, spaik
22 PHOTOGRArHED SPECTRA.
bright. Spectrum peculiar as containing so little trace
of the air lines, and for the fuzzy expansion of the
principal lines. The lines generally are not confined to
the margin, but cross the spectrum. Lecoq de Bois-
baudran (Plate Vli., Chlorure de Barium dans le gaz)
gives bands at 4974, 4873, 4794, and a barely visible
line or band somewhat beyond. Dr. Watts gives bright
hues or bands 4934, 4898, 4553, 4524, and 4130.
From an examination of these last, I think that our
spectrum (for want of the air lines) has been some-
what wrongly positioned.
If the Scale be advanced a httle to the right, so
that the second bright hne in the spectrum coincides
with 4898 (4900) on the Scale, the other Unes will be
found to fall fairly into their places, in accordance with
Dr. Watts' figures.
Second Spectrum. Beryllium (Glucinum) Arc. —
Metal in powder in carbon cup. Arc short. Dr. Watts
gives two bright lines for Glucinum, 4572 and 4488.
These are not prominent in our spectrum, which is
chiefly characterised by the bright hues between ' spark '
and F, and by other fine lines scattered through the
spectrum. The spectrum, however, bears so great a re-
semblance to meteoric iron and meteorite (Plate X.),
that there was found reason to suspect iron as form-
ing the principal part of it. Upon testing the metal
powder, it was found to contain iron as an impurity
in considerable quantity.
Third Spectrum. Boron Arc. — Graphitoid in car-
bon cup. A dense glass-like crust of oxide formed
DESCRIPnON OF PLATES. 23
on the upper carbon, which interfered with the current,
and had to be frequently cleared off. Arc short and
uncertain. The evidence of the spectrum is mainly
towards the red end, where absorption bands seem
traceable.
FouETH Spectrum. Calcium Spark. — ^Pieces of
metal in the clips inclined to fuse quickly. Spark
fairly bright. This failed as a Calcium spectrum. The
principal lines, a double one at about 4935, and others
at about 4830, 4750, 4710, and 4060, are those of zinc.
Upon testing the specimen of the metal, zinc was found
present in considerable quantity.
PLATE V.
First Spectrum. Cadmium Spark. — Small pieces
of the metal in clips, exposure moderate, plate rather
weak, but clear of air lines.
Second Spectrum. Cadmium Arc. — Pieces cut
from small bars in carbon cup. Clouds of yellow oxide
formed. Arc moderate. Metal burnt away quickly,
Lecoq de Boisbaudran [Plate XX., Chlorure de Cad-
mium], gives principal lines at 5085, 479 ), 4677, and
a moderate one at 4414.
These three principal lines appear in our arc
spectrum, with an additional conspicuous line about
4060. A line inflated at each end also appears at about
4425 in the spark spectrum, which may be Lecoq de
Boisbaudran's 4414.
Third Spectrum. Arc between Carbon points.
24 PHOTOGRAPHED SPECTRA.
Fourth Spectrum. — A paper print from the plate
of Spectrum 3, with all the lines which could be in
any way seen on the glass negative ruled out.
A description of the preparation of the carbon
points has been already given in the Introduction.
The Third Spectrum is an example of the plates ob-
tained from the points alone. This plate contains,
besides those that show in the print, a number of very
faint hues seen only when it is held up to the light.
A good paper print was obtained from this plate, and
on this was ruled out all the hues that could be traced
on the negative. A reversed copy of this is shown
in the Fourth Spectrum. The lines are presumably
those arising from the points, and a peculiarity of oiu:
arc spectra in general seems to be that while these
lines are all more or less present in each arc spectrum,
the number and intensity differ much. They appear
also to depend for number and intensity, to a con
siderable degree, upon the metal or other substance
burning in the arc, so that spectra of the same metal
almost invariably contain, in addition to the metal lines,
point lines of the same extent and character. It is this
fact that seems to give to each spectrum its individuality
referred to in the Introduction.
PLATE VI.
FrasT Spectrum. Spark in Coal Gas. — ^For this
spectrum the same spectroscope was employed as in
the case of the metals. A glass tube with a bulb
DESCRIPTION OF PLATES. 25
blown in the centre, of the form here shown (^ size),
with platinum wires fused into the bulb was selected
3
to pass the spark through. One end of the glass tube
was connected, by means of elastic tubing, with the gas
jet in the room. The other end of the tube was also
joined to tubing which conveyed the gas out of the
room into the air, after passing through the bulb.
The two platinum wires were connected with the large
coil and condenser, and while the spark was striking
across the bulb (vertical with the slit) a current of
coal gas at ordinary pressure was kept flowing through
the tube. The spark was bright and slightly blue in
tint. Carbon was soon deposited on the bulb. The
spectrum shows a set of carbon hues, the two brightest
at about 4580 and 4220, and also the hydrogen line
h considerably expanded. This last line also has the
appearance of being either double, or reversed, in the
centre. The line 4220, and its accompanying group of
fine lines on the right, occupy about the same place as
a set of bright lines in the arc spectrum. They are
however not identical, the lines in the coal gas diminish-
ing in distance from each other towards the bright line,
while in the arc the lines diminish towards the violet,
(see a better enlargement of this negative on Plate
26 ' PHOTOQKAPHED SPECTRA.
XXVI., Second Spectrum). It is curious that we ob-
tained this sharp line spectrum on only one occasion,
though we subsequently took several other plates under
similar conditions of apparatus and spectroscope.
In the subsequent plates the line 4580 was replaced
by a misty band, with a double or reversed appearance
similar to the hydrogen line in our plate. Of its
accompanying set of lines towards the violet, one
only, the detached one nearest to the violet, remained.
Line 4220 nearly disappeared, and remained only
misty and indistinct ; while the group lines accompany-
ing it were quite gone, and a bright broad band reach-
ing to the hydrogen line took their place.
The hydrogen line h was not so much expanded as
in our spectrum, and a continuous spectrum crossed by
two narrow bands or broad lines, and two other faint
lines (Hydrogen?) appeared beyond it towards the
violet. See also a plate of the same spectrum taken
with the gas spectroscope C, Plate XXVIL Second
Spectrum, and a print from the original plate, from
which the present enlargement was made, Plate
XXXIII. Fourth Spectrum.
The plates of the subsequent spectra before de-
scribed were altogether more misty and less defined
than our first spectrum.
Second Spectrum. Chromium Arc, — Metal powder
in carbon cup, some scintillation during combustion.
Lecoq de Boisbaudran gives [Plate XVI., Sesqui-
chlorure de Chrome], a very bright line at 5205, a
double one at 4649, a band of indistinct rays at 4343,
DESCRIPTION OF PLATES. 27
and three well-marked lines at 4290, 4275, and 4255.
The line 5205 does not appear in our spectrum, (the
outside line towards the red is a carbon one). The
other Unes are easily distinguished.
A set or band of close lines is also to be noticed at
about 4540.
Thied Spectrum. Cobalt Arc. — Small piece of
metal in carbon cup, arc moderate. Lecoq de Bois-
baudran [Plate XIX., Chlorure de Cobalt] gives a list of
twenty-one Hues in the part of the spectrum comprised
in our photograph, distinguishing for brightness 4868,
4840, 4815, and 4533. In our spectrum the lines show
pretty much of equal intensity, and it is somewhat diffi-
cult to separate them from the carbon lines.
Fourth Spectrum. Copper Spark. — Small pieces
of wire, spark tinged green, spectrum poor, principal
line crosses a part of the air spectrum deficient of bright
lines, at about 4280.
PLATE VII,
First Spectrum. Copper Arc. — Stout pieces
of copper wire used as terminals, arc narrow, brilliant
green in tint and of moderate length.
Second Spectrum. Copper Arc. — Small bead of
prepared wire, an aUoy of gold, silver, and copper in
the carbon cup. The wire was prepared by a jeweller
as an equal part alloy of pure gold and silver, but it
subsequently proved that the gold was adulterated with
copper.
28 PHOTOGRAPHED SPECTRA.
{Note, — ^The images of these two spectra are not
of the same actual size, the carbon arc being some-
what the larger, and allowance must be made for this
in comparing them with each other and with the
Scale).
In the case of the alloy, the copper, though so inferior
in quantity, seems to have mainly appropriated to itself
the spectrum. The gold and silver lines are very faint,
but they may be traced by comparison with the spectra
of these metals. (See also Plate XV., Spectrum Silver
and Copper Arc, where copper again monopolises the
spectrum).
Most (but not all) of the lines in the First Spectrum
appear in the Second Spectrum, mixed with a few of
the principal carbon or point lines. The bright single
line about 4400 in the first spectrum appears double
in the second spectrum.
The very conspicuous double line in the first
spectrum at about 4075 is replaced by a single bright
one, with faint companion in the second.
Lecoq de Boisbaudran gives [Plate XXIV.,
Chlorure de Cuivre en solution], a long list of copper
lines, including the three characteristic ones (5218,
5153, and 5106), seen on the extreme left of our
spectrum.
He also gives on the same plate the spectrum of
Chlorure de Cuivre dans le gaz, with brighter groups
towards the violet. These spectra do not in general
character accord with ours.
Thied Spectrum. Didymium Arc, — ^Powder in
carbon cup, arc short, spectrum full of many coarse
DESCRIPTION OF PLATES. 29
lines of the same character; with traces, especially
towards the red and the centre, of absorption bands.
The carbon lines are either absent or so obscured by
the metal spectrum as almost to cease to serve as
guides in masking. Lecoq de Boisbaudran gives [Plate
Xin.] two absorption spectra of Didymium, neither of
which readily compares with ours in lines or character.
Fourth Spectrum. Erbium Arc. — ^Powder in
carbon cup, a bead of the fused metal insisted on
adhering to the negative pole, the arc being then longer
than when the metal remained in the cup. When the
metal was burnt in the cup the arc was brightest.
The spectrum is characterised by a considerable number
of bright lines, with many very fine ones between ; the
carbon lines are also in this case either absent or very
much obscured, so that position on mask is doubtful.
Lecoq de Boisbaudran gives [Plate XIV.] a spectrum of
* Erbium emission,' which does not assist in examining
ours. Dr. Watts gives a joint spectrum of Erbium and
Yttrium, with some lines common to both metals. Our
spectrum of Erbium does not accord with that of
Yttrium, Plate XIX., in lines or general character.
We found in our cabinet, a specimen labelled Terbium,
of which we also photographed the spectrum. On
comparing it with oiu- present spectrum of Erbium,
(except that the one spectrum has a little less glare
than the other) the two spectra were found absolutely
and line for line coincident.
Every line is exactly repeated in each plate, and the
relative intensities of the lines are preserved in each
spectrum in the most accurate manner.
30 PHOTOGRAPHED SPECTRA.
PLATE Vni.
First Spectrum. Gold Arc, — Small lumps of metal
in the carbon cup. Arc short. Spectrum fairly clear of
point lines. Lecoq de Boisbaudran gives [Plate XXVI.
Chlorure d'Or en solution] lines at 5063, 4812, 4793,
4608, 4490, 4437, 4338, 4314, 4064. The lines 4812
and 4064 are recognised in our spectrum, as also a
strongish line about 4570.
Second Spectrum. Indium Arc. — Small piece of
the metal cut from bar in carbon cup, arc moderate,
spectrum with a good deal of glare, point lines indis-
tinct. Two principal broad and expanded metal lines
read off at about 4515 and 4100, (Lecoq de Boisban-
dran gives Plate XXI., Sels dlndium, 4511 and 4101).
For spark spectrum of Indium, see Plate XVI., Third
Spectrum.
Third Spectrum. Indium Arc. — ^Piece of metal in
carbon cup. Arc short. Spectrum bright. Point lines
long in centre. Note group of very fine lines at ex-
treme left towards the red, (centre about 4990) with
two dark spaces to right of them, also two bright lines
about 4550. Dr. Watts gives a spectrum of * Iridium,
and Euthenium,' with lines (Kirchhoff) 6347, 5449,
and 5299. For our spectrum of Euthenium, see
Plate XTV"., Second Spectrum. The two spectra
certainly have a very close general resemblance. Note
the group of four lines towards the red end and the
outlying short line at the extreme violet end, common
to both.
DESCRIPTION OF PLATES. 31
Fourth Spectum. Iron and Copper Spark, — Wires
of the metals in the clips, condensing lens, in front of
slit, slit wide. Image rather coarse. Iron lines pro-
jecting in several places beyond the upper edge of the
specflrum. Copper line at about 4280 seen projecting
on lower edge of the spectrum.
PLATE rS.
First Spectrum. Copper and Iron Spark, — Same
as last (Iron and Copper), but metals reversed in chps,
no condensing lens, slit wide and image confused, but
lines can be traced through the glare.
Second Spectrum. Iron Arc. — Eeduced powder
in carbon cup. Arc moderate, much scintillation.
Thirty cells Grove only used, sKt rather wide. Spec-
trum imperfect, but introduced to show how battery
power may vary general aspect of the spectrum. Note
broad dark space about centre of spectrum, also glare
of light towards the red, with group of lines at ex-
tremity of spectrum in that direction.
(This spectrum is not positioned to the. Scale, but
can easily be compared by eye with the next).
Third Spectrum. Iron Arc. — Eeduced powder in
cup forty cells Grove. Slit fine. Spectrum much more
uniform than last, point lines absent or indistinct.
Lecoq de Boisbaudran gives [Plate XVIII., Per-
chlorure de Fer en solution Etincelle] a spectrum com-
prising a set of groups of lines in the violet separated
from those at the other end of the spectrum by a
32 rHOTOGRAPHED SPECTRA.
blank space. This blank space is also seen in our
photograph separating the four characteristic lines to-
wards the red end of the spectrum from the main body
of lines towards the violet.
The lines towards the red in our spectrum evidently
correspond with Lecoq de Boisbaudran's 4959, 4923,
4891, and 4874. Our spectrum is slightly out of
position on the mask ; but if the scale be moved a
little towards the left, so that the first of the set of
these four lines be made to coincide with 4959 on the
scale, most of the other lines in Lecoq de Boisbaudran's
list may be picked out.
Fourth Specteum. Iron and Selenium Spark. —
This spectrum is introduced to show the iron lines in
spark. Two small pieces of Selenium were placed in
the steel clips. When the spark passed, in lieu of
striking from pole to pole, it flew with a long and
bright flash across the surface of the selenium melting
it in its way.
On examining the spectrum, it was found a com-
bined one of air, selenium, and iron, some of the lines
of the latter projecting in a most marked manner be-
yond the edges of the spectrum. These lines were
evidently due to the clips. We tried Selenium two or
three times, and always with the same result as to
behaviour of the spark.
Now and then it seemed to cross between the poles,
but ordinarily it preferred the longer route across the
surface.
The Spectrum of Selenium will be found referred
to in its order further on.
DESCRIPTION OF TLATES. 33
PLATE X.
First Spectrum. Meteoric Iron Arc.
Second Spectrum. Meteorite Arc.
Three specimens purchased of Mr. James E. Gregory
were used m the arc : —
No. 1. Meteoric Iron. Atacanna 1827.
No. 2. Meteoric Iron. Tolucca 1784.
No. 3. Piece of Meteorite. Ausson 1858.
They all burnt with much scintillation in the car-
bon cup. The spectrum of No. 1 when examined was
found identical in all respects with the spectrum of Iron
in arc (third spectrum, last plate) and might have been
taken for the same photograph.
No. 2 and No. 3 (the plates which are printed) also
gave spectra evidently of iron, but differing from the
spectra of No. 1 and of Iron in arc in last plate and
from each other. Each of th^m is characterised by
the large number of sharp and fine lines, which more
especially in the case of the meteorite, intermediately
fill up and occupy nearly the whole spectrum. Some
of these lines it is true may be traced very faintly in
our spectrum of Iron on Plate IX., but they appear to
come out relatively stronger and brighter in our present
plates. Meteorite seems also to differ from meteoric
Iron in the greater length of spectrum (note group of
fine lines to the extreme left), and in the greater
number of its fine lines generally. This will be par-
ticularly noticed about the brighter and wider part of
D
34 PHOTOGRAPHED SPECTRA.
the spectrum where the coarse and strong lines
mainly prevail. Some of these, which have dark in-
tervals in the case of meteoric Iron, are connected by
and filled up with fine hues in the case of meteorite.
Note also a thick double line about 4048 in meteorite,
which is doubtfully represented in the meteoric Iron
spectrum.
Third Spectrum. Lead Arc. — ^Piece of metal in
carbon cup. Arc moderate.
Fourth Spectrum. Lead and Antimony Spark, —
Small lump of antimony in one clip; small bar of
lead in the other. Current reversed at half exposure.
Lecoq de Boisbaudran gives [Plate XXTTT., Plomb
m^tallique Etincelle] lines at 5044, 5003, 4386, 4245,
4167, 4056, noting 4056 as very characteristic. Lines
appear in our arc spectrum corresponding with his
5003, 4386 (4245 and 41()7 are mixed up with the
point Unes) and very prominently indeed 4056. We
have lines also about 4825, 4750, and 4700, which he
does not give. In the spark spectra we get prominently
Boisbaudran's 5044, a bright line about 4780, a tre-
mendous one at ,4400, another still larger at 4250
(Boisbaudran 's 4245 ?), and lastly 4056, very sharp
and well defined.
The wonderful inflation and flare of the two lines at
4400 and 4250 are to be noted. In the case of the
latter line the flare appears unequally towards the
violet side. Other smaller lines are in the spectrum
(see Magnesium and Lead, second spectrum on next
plate).
DESCRIPTION OF PLATES. 35
The Antimony Spectrum has been already described,
but note the glare of light and thickening of the lines
before referred to in reference to that spectrum.
PLATE XI.
First Spectrum. Lead and Magnesium Spark, —
Small bar of Lead in clip ; Magnesium ribbon cut to a
point in other clip. Current reversed at half time.
Second Spectrum. Same as above, except that the
metals are reversed in position. A condensing lens
was used in front of slit.
Third Spectrum. Magnesium Spark. — A piece of
magnesium ribbon, cut to a point, used in each clip.
Slit '001 inch. Exposure fifteen minutes.
Fourth Spectrum. Magnesium Arc ^Piece of
ribbon coiled up in the carbon cup, quickly ignited,
and long arc obtained ; much oxide formed.
Lecoq de Boisbaudran gives [Plate XII. Chlorure de
Magnesium] lines as follows : group, 5183, 5172, 5167,
very bright (6 in solar spectrum), then a band of rays,
commencing with 5006 and ending with 4958, and
then single lines, 4705 and 4483.
Our first two spark spectra are mainly conspicuous
for the great blaze of light at about 4500. This is
very marked and characteristic, and extends in each
case considerably beyond the margin of the spectrum.
In our third spectrum (Magnesium ribbon in each clip)
the print is cut off in vertical by the limited width of
mask ; but upon examining the original plate the glare
D 2
36 PHOTOGRAPHED SPECTRA.
of light on the lower margin of the spectrum at 4500
is distinctly traced to extend beyond the margin of the
spectrum to a length equal to the glare itself (nearly
half the width of the spectrum) as a single hne ter-
minating in a minute knob or inflation (limit of prism
surface ?). Two bright lines at about 4725 (Boisbau-
dran's 4705 ?) and 4360 are also seen to project
beyond the spectrum, though not to so great an extent.
Both of these last lines appear to be repeated in the
arc spectrum, while the large 4500 is missing there.
The group b in solar spectrum is seen in both spark
and arc spectra as a double line only (tested by this,
our Scale is a little too much extended towards the
extreme left). Then in the arc comes the band of
lines at 5006, then 4725 and 4360, and lastly two
bright lines at about 4245 and 4180. The other and
fainter lines in the arc seem due to carbon.
PLATE Xn.
First Spectrum. Manganese Arc, — Powder metal
in the carbon cup ; arc moderate, with some scintil-
lation, taken with battery of 30 Grove cells.
Second Spectrum. Same, but taken with battery
of forty Grove cells. Lecoq de Boisbaudran's Plate
XVn., Chlorure de Manganese en solution, Etincelle
courte, is found closely to compare with our spectrum
in principal lines, and the two spectra were selected to
form a scale by comparison and interpolation as
described in the Introduction. The lines given by
DESCRIPTION OF PLATES. 37
Boisbaudran are 4825, 4784, 4766, 4755, 4738, 4727,
4710, 4502, 4462, 4437, 4415, 4282, 4266, 4260,
4237, 4084, 4063, 4047, 4039. These were also com-
pared with Dr. Watts' list of (Huggins') lines of Man-
ganese ; and then those most easily recognised with
corresponding ones in our spectrum were used as
materials for the Scale. The principal lines are easily
sorted out by the aid of the upper spectrum.
Third Spectrum. Mercury Spark. — Globule of
the metal in a small glass cup with Platinum commu-
nication passing tlirough the bottom of the cup.
Platinum wire electrode above. Exposure twenty
minutes. Spark brilliant and rapid.
The spectrum is characterised by the misty and
indistinct appearance of the air hues. They are, how-
ever, sufficiently defined to indicate position of the
metal lines, these last being coarse and thickened.
Lecoq de Boisbaudran gives [Plate XXV., Bichlorure
de Mercure] a strong line at 4357, and two other lines
at 4078 (faint), and 4047 : 4357 is well marked in our
spectrum, also 4047, and there is an additional strong
line at the end of the spectrum about 3985.
Fourth Spectrum. Molybdenum Arc, — Powder
metal in carbon cup. Soon formed a bead, which re-
mained quiet at bottom of the cup. Arc long, and
gave a bright lambent glow rather than a brilliant
stream.
Dr. Watts gives hues (Thalen), 4979, 4867, 4829,
4818, 4757, 4730, 4706, 4536, 4475, 4433, 4411,
4380, 4326, 4277,
38 PHOTOGRAPHED SPECTRA.
The group 4737, 4730 and 4706, is easily dis-
tinguished, and other of the foregoing hnes may be
picked out in the clearer parts of the spectrum.
PLATE Xin.
FiKST Spectrum. Nickel Arc. — Small pieces of metal
in the carbon cup, arc short, spectrum tolerably clear
of point lines. Leccq de Boisbaudran gives [Plate
XrX., Chlorure de Nickel] a long hst of hnes com-
mencing with a strong one 4984, and ending at 4288,
and with characteristic ones at 4715 and 4401.
4715, 4647, 4606, 4550, 4461, and 4401 (strong),
may be picked out in the clearer part of our spectrum
towards the red end. Notice also a sharp bright line
in a clear space about 4000.
A small bottle without a label containing a powder
was found in our cabinet. The spectrum when photo-
graphed was at once easily identified with our present
plate.
Secoist) Spectrum. Niobium Arc, — Powder metal
in carbon cup, arc moderate. Dr. Watts quotes
Thalon as stating that the lines of Niobium are too
faint to be measured satisfactorily.
Our spectrum, however, after excluding the carbon
lines has a considerable set of bright ones which must
belong to the metal. These may be seen at about
4861 (F), 4615, 4590 (strong double), two bright lines
with a fine one between them about 4435 and 4405, a
set of three lines, (a single and then a double) about
DESCRIPTION OF PLATES. 39
4260, a bright one with shading towards the violet, at
4100 (A), (it is curious that F and h places of
hydrogen lines should each have prominent lines
falKng in the same or very closely approximate
positions in this spectrum), a thickened or double line
about 4050 (position also of a carbon line), and a
double one near to the last about 4040.
Third Spectrum. Palladium Arc. — Piece of metal
in the carbon cup, arc moderate, spectrum showing
carbon lines indistinctly.
Lecoq de Boisbaudran gives [Plate XXVIL,
Chlorure de Palladium,] a set of lines at 5118, 5114,
and 5111, then single lines at 5063, 4969, and
4917, then three well-marked lines at 4874, 4818,
and 4788, then one at 4475, then a strong one at 4214,
concluding with two at 4170 and 4088. The hues at
5111 and 5063, and the stronger ones at 4874, 4818,
4788, 4475, and 4088, may be all picked out from our
spectrum. A carbon line between H^ and H^, seems
also to have another by its side not belonging to it.
Note also extension of spectrum towards the violet, as
in the cases of Iridium and Euthenium.
Fourth Spectrum. Platinum Arc. — Small roll of
foil in the carbon cup, arc short, spectrum poor,
mainly carbon lines. Lecoq de Boisbaudran gives
[Plate XXVII., Chlorure dePlatine] a set of lines com-
prising (with others) 4554, 4524, 4501, 4415, 4390,
4118. These seem distinguishable in our spectrum,
and there are also two bright lines about 4250, not
given by Boisbaudran.
40 PHOTOGRAPHED SPECTRA.
PLATE XIV.
First Spectrum. Rhodium Arc. — ^Kece of metal in
the carbon cup. Spectrum of even character, with
many sharp metal lines. Point lines not prominent,
except in the centre of the spectrum,
Here again Dr. Watts quotes Thal^n, that the lines
are too faint to measure, but many may be picked out.
from our print. Note especially two sharp hues
between 5000 and 4950, a double line near F, a line
about 4590 near two point hues, another about 4420,
with two fine ones towards the red, and a strong one
near a carbon line about 4100. Other lines will also
be found, intermediate of the point lines, in the region
extending from 4400 towards the red end of the
spectrum. Note also a set of three lines (strongest
towards the red), about 4265, and a strong set of three
lines of equal intensity, the centre one about 4125.
N.B. In this and other cases in which no authentic list
of lines is referred to, it is useful to test the spectrum
by the carbon points ruled out, Plate V., so as to
eliminate the point lines from the spectrum.
Second Spectrum. Ruthenium Arc. — ^Hece of
metal in the carbon cup, arc short. This spectrum has
already been referred to under the head of ' Iridium.'
Third Spectrum. Selenium and Tellurium. —
Small piece of these in each clip, current reversed
at half.
Fourth Spectrum. Selenium and Aluminium. —
Small piece of Selenium in one clip. Aluminium
DESCRIPTION OF PLATES. 41
wire in the other, current not reversed. The Aluminium
spectrum, Plate II., has been described ante^ p. 19. It
is, however, from the absence of air hues, well shown
in the present print. See also Plate XVII , Second
Spectrum, Titanium and Aluminium. The spark passed
more freely than when both electrodes were of Seleniiun,
but still played over the surface of the Selenium partly
fusing it. (Compare Iron and Selenium Spark, Plate
IX., and note the Iron lines in each of the present
spectra as affecting the Selenium pole of the spec-
trum).
In the third spectrum the Selenium has partly
melted away, and the spectrum is doubled.
The spectrum of Selenium is distinguished by its
quantity of very fine sharp lines towards the red
running into bands towards the violet. Many of these
lines in our plates are too fine to print satisfactorily.
The lines are best seen in the spectrum Iron and Sele-
nium, Plate IX., the bands in our two present plates.
In each case the metal Unes and bands follow
the ordinary rule of being found at the edges of the
spectrum. There is an inclination to mistiness or glare
at the poles, as in the case of Antimony. Dr. Watts
gives from Pliicker a long list of close lines towards the
red end, and of bands towards the violet end of the
spectrum.
We pick out conspicuously in our spectrum bright
lines at about 5000 (Plucker's 4994 ?), 4850 (Plucker's
4845 and 4840?), 4880 (Plucker's 4776?), 4600
(Plucker's 4606 ?), and 4425. The bands towards the
42 PHOTOGRAPHED SPECTRA.
Violet are also well seen about 4225, 4190, and 4140.
The two sharp lines about 4015 and 3998 are Iron
lines.
PLATE XV.
First Spectrum. Silver Spark, — Small bars of the
metal in clips. Spark short and white, edged with
greenish glare. Exposure twenty minutes.
Second Spectrum. Silver Arc ^Piece cut from
bar of the metal in the carbon cup. Soon became red
hot, and melted into a bead, which rotated in the cup,
and from which the arc sprang. Arc moderate, and
tinged with green.
Lecoq de Boisbaudran gives [Plate XXV., Azotate
d' Argent en solution] a set of lines commencing with
two very strong ones at 5464 and 5208, a band or set
of lines at 5022, 4997, 4968, and following on with
4669, 4622, 4570, 4518, 4475, 4434, 4396, 4208.
In our spark spectrum we have in our plate a line
about 5150, which has not printed. 4997 seems indi-
cated by the breadth and strength of the ' spark ' line.
Four air lines, 4960 to 4900, are unusually strong.
4669 is marked by projecting slightly beyond the
spectrum. The other lines do not show. The battery
and coil power does not seem to have been sufficient
to bring out the metal lines satisfactorily. In our arc
spectrum we find brilliant lines corresponding with
5208 (our Scale, as we have noticed before, is a little
too much extended towards the red in this part of it).
DESCRIPTION OF PLATES. 43
4690 (Boisbauclran's 4669?), 4480 (his 4475?), and
two very strong lines, about 4215 (i)lace of a point
line), and 4050.
Third Spectrum. Silver and Copper Arc. — A
small piece of metal wire in the carbon cup. This was
procured from a jeweller, and warranted pure as
being the silver wire employed by the natives of India
in making filagree and other ornamental work. It had,
however, I thought, a shghtly reddish tint, and upon
combustion (behaving much the same as the last spe-
cimen) the spectrum proved a mixed one of copper and
silver.
For some reason which we do not trace, the
spectral image is smaller in size than that of Silver arc.
The enlargements are both once, and the difierence is
in the original plates. It is however almost exactly
the same size as Copper arc, first spectrum, Plate VII. ;
and this last can be used to distinguish the copper hues
in our present spectrum. They mainly usurp the spec-
trum, but the Silver line at 5208 (apparently doubling
the copper line 5218), and those at 4215 and 4050,
are easily recognised.
Fourth Spectrum. Solar Spectrum, — This spec-
trum was photographed mainly for the purpose of
comparison with the metal spectra in regard to the
dispersion of the spectroscope, but also as a sort of
check upon our Scale, see Plate XXI., Scale and Solar
Spectrum. The solar lines are fairly seen, but they are
too fine and close together, and on too small a scale to
make them available for comparison with the coarser
44 PHOTOGRAPHED SPECTRA.
metal lines. Indeed, this comparison did not form
part of our intended work. The photograph was
taken on a fine, but not absolutely clear, day in winter
with the sun near the meridian. A table was arranged
in the open air, facing the south, with the spectroscope
and camera as used for the metals upon it, the photo-
grapher's back being to the sun. The slit was made
as fine as possible, and a plane mirror and condensing
lens were used to throw the sun's image in a parallel
direction upon it. The slit was covered with a cap,
which was removed when it was desired to take the
photograph. Of the two successful plates, one was
exposed three seconds, the other two seconds. The
last has the lines sharpest and most distinct. This
plate indeed is very sharp, and the lines are well de-
fined ; but it is difficult to get as good an eflfect in the
prints.
The lines in the plate are seen nearly as far towards
the red as b. In the print they stop short midway
between h and ' Spark.' F, G, and h are well marked.
The print stops short at H ^ ; but in the plate a
br'ght space with four dark lines succeeding H ^ is seen,
and then the spectrum terminates abruptly with the
dark interval representing W.
PLATE XVI.
First Spectrum. Strontium Spark. — ^Pieces of metal
in the clips. Spark bright, metal melted rapidly.
Spectrum (like Barium) characterised by the absence of
DESCRIPTION OF TLATES. 45
air lines, and by the broad fuzzy character of the
metal hnes. Lecoq de Boisbaudran gives [Plate IX.,
Chlorure de Strontium en solution] four lines (second
and fourth the strongest) with places as follows : —
4307, 4215, 4163, 4079.
Assuming the first expanded line to be 4307, and
placing the Scale accordingly, the other three lines
4215, 4163, 4079, towards the violet, fall into their
proper places. The bright unexpanded line towards
the left of 4307 seems to be an air line.
Second Spectrum. Tellurium Sparky (see also
Plate XIV., Selenium and Tellurium Spark). — Eough
pieces in each of the clips, which wore away
quickly, the spark occasionally running to the clips.
Spectrum characterised by comparative absence of air
Knes and a general likeness to Selenium without its
very sharp lines. Dr. Watts gives lines (Thal^n)
4895, from his own observation 4866, 4832, 4785, then
three (Huggins') 4709, 4664, 4652, then one of his
own 4602, and then (Huggins') 4599, 4544, 4479,
4352, 4302, 4259, 4063. In oiu: Spectrum, lines or
bands are well traced between 4900 and 4650 in
places nearly corresponding with some of the above, as
also a band at about 4485 (4479 ?) and some bright
bands in the margins of the lighted-up region 4350 to
4225.
The line or band 4063 seems also recognisable on
the lower margin of the spectrum.
Third Spectrum. Thallium and Indium Spark
(for Indium Arc, see Second Spectrum, Plate VIII.)
46 PHOTOGRAPHED SPECTRA.
— Small pieces of the metal in the clip, current reversed
at halt^ spark bright. Spectrum characterised by
absence of air lines, and distinctness of metal lines.
On the print, seven lines belonging to Thallium may
be counted. Two if not more, finer ones appear on
the plate. Seven lines at least are seen on the
Indium margin of the spectrum, including the large
ones seen in the Arc Spectrum of Indium which, as
in the case of the arc, are very sharp and well defined
and run nearly across the spectrum. (This spectrum
was originally a short image, and is also very slightly
underenlarged so that the whole is slightly shorter
than the Indium Arc Spectrum. Allowance must be
made for this in placing the Scale.)
Lecoq de Boisbaudran gives no lines for Thallium
in our part of the spectrum, and only the two referred
to ante for Indium. Dr. Watts gives for Thallium, on
his own, Huggins', and Thal^n's authority lines at 5153,
5085, 5078, 5054, 4980, 4945, 4893, 4767, 4737,
4112. Our Scale indicates on our spectrum lines which
correspond with 5153 (scale too much extended in that
part), 5078, and notably 4767 (very bright and broad).
A line is shown about 4300, and one about 4120 (4112?)
is faintly indicated. Two lines appear in the plate
about 4945 and 4893 which do not show in the print.
Dr. Watts gives for Indium (Thalen) 5532, 4509,
4101. Allowing for the difference in size of the
toage before referred to, 4509 and 4101 are easily
distinguished sharp and well defined and projecting
beyond the spectrum ; 4532 is not definitely traced.
DESCRIPTION OF PLATES. 47
but on each side of 4700 broad and bright hnes or
bands are seen. Note also a bright line about 4090,
with a faint one beyond. A shght flare seems to run
along the Indium margin of the spectrum.
Fourth Spectrum. Thallium Arc, — Piece of the
metal in the carbon cup. Arc moderate, metal very-
soon volatilised, and we doubted whether any trace of it
was impressed upon the spectrum. A fine line at the
extreme red end of the spectrum about 5250, and
others about 4610, 4405, 4260, and 4100, are however
intermediate of the point lines ruled out. They may
be metal lines, but their character is not what one
would expect in that case.
PLATE XVn.
First Spectrum. Titanium. Spark. — Two pieces of
ore in the clips. Spark occasionally gave a reddish
flare.
Second Spectrum. Titanium^ Aluminium^ and
Palladium., — Palladium in clip, for upper pole. Lower
pole a small Aluminium cup, (with Platinum wire let
through the bottom) filled with Titanium in powder.
Current reversed half time. Spark long and bright,
and occasionally played round edge of the cup, fi:-om
which some of the powder was from time to time
ejected. Aluminium spectrum due to the cup very
apparent on upper edge of spectrum in print. Air lines
in first spectrum weak towards the red end.
Third Spectrum. Titanium Arc, — Metal powder
48 PHOTOGRAPHED SPECTRA.
in the carbon cup. Soon formed a bead, which remained
quiet in the cup. Arc long and lambent.
Dr. Watts gives (with wave lengths by Thal^n) a
long list of Titanium lines, most of them of considerable
intensity, and in some parts of the spectrum very
closely packed together. Between 5300 and 4163 we
count no fewer than 149, the greater number being of
the higher range in intensity.
Our spectrum contains several groups of fine lines
close together. One to the extreme left at about
5025 to 4975. A wider set, about 4925 to 4850 ;
another wide set, 4700 to 4625. A set of fine bright
lines 4560 to 4525, and another set about 4390 to
4340. Single bright lines are distinguished about
4775, 4550, 4460. A set of five of about equal
distance apart between 4450 and 4400, and a single
one about 4300. The single ones may be Thal^n's
4779, 4549, 4468, and 4299, the first being of Watts'
intensity 6 and the three last his intensity 10. Going
back to the spark spectra, we fail to trace much evidence
of the metal lines. In the first spectrum the principal
evidence of the metal is confined to a few sharp faint
lines partly crossing the spectrum. 4549 is thus seen,
and two others about 4420.
The strong well-defined lines in the bright part of
the Spectrum are Iron (hence the red flare in the
spark). In the second Spark Spectrum no more is
seen, the strong lines on the upper margin being those
of Aluminium.
Dr. Watts gives lines for Palladium (Huggins and
DESCRIPTION OF TLATES. 49
Thal^n) 5062, 4876, 4818, 4787, 4474, 4278, 4212.
In our spectrum 4876 is indistinctly traced, then a
line thickened at margin about 4710, 4474 seems
well marked. About 4300 is a conspicuous bright line
projecting beyond the spectrum (4278?) with others
near it. A bright Kne is well seen at 4225 (4212 ?)
and another not so bright at about 4165. A faint line is
also seen beyond H^ which may belong to the metal.
Fourth Spectrum. Tin Arc. — Some granular
metal in the carbon cup. Arc short, spectrum con-
spicuous for a few metal lines and the brightness of the
lines in the region of H^ and H'^. All the other point
lines (except 4225) indistinct. Lecoq de Boisbaudran
gives only one line in our part of the spectrum which
is easily recognised, 4526 ; but note also a line about
4100, which does not seem to be a point line, and which
has the peculiarity of only partly crossing the spec-
trum.
PLATE XVIII.
First Spectrum. Tin and Zinc Spark, — Small Zinc
bar in one clip. Granular tin same as used in arc
in small glass cup, with platinum wire connection for
other electrode, current reversed at half, slit rather
wide.
Second Spectrum. Tin and Zinc Spark, — Second
plate of same.
Dr. Watts gives for Tin (Thalen) 5100, 5021,
4923, 4858, 4585, 4524, (Boisbaudran's 4526). The
First Spectrum shows towards the red end 5100 and
E
50 PHOTOGEAPIIED SPECTRA.
4923. Then referring to the second spectrum, we get
4858, 4605 (4585?), 4550, 4540, and about 4515
(4524 ?). The one bright hne in the arc (4524) is
but faintly represented in the spark spectrum.
Third Spectrum. Uranium Arc. — Powder metal
in the carbon cup. Arc moderate, some scintillation.
Spectrum much glared, with many indistinct rather
coarse lines, from among which the point lines about
H^ and ff and 4225 shine out conspicuously. Dr.
Watts gives a set of lines (Thalen), among which 4472,
4393, 4374, 4362, and 4340, may perhaps be selected
in our spectrum.
Fourth Spectrum. Vanadium Arc, — ^Powder
metal in carbon cup. Arc moderate. A splendid spec-
trum, characterised by a family likeness to Titanium,
but with a yet greater quantity of bands of close sharp
lines. Dr. Watts gives a list (Thalen) of thirty-
two lines between 4881 and 4085 (about where our
spectrum begins and ends). Groups of lines are found
with centres about 4843, 4585, 4389, and faint lines
extending from 4130 to 4085. This will be seen to
very closely agree with our spectrum, in which the
groups quoted (with others) stand out very beautifully.
PLATE XIX.
First Spectrum. Wolfram Arc. — ^Powder metal
in carbon cup. Arc moderate. Spectrum somewhat
like Uranium in character, but with brighter lines and
longer.
DESCRIPTION OF PLATES. 51
Dr. Watts gives lines (Thalen) for Tungsten 5014,
5007, 4981, 4887, 4842, 4680, 46G0, 4659, 4302,
4295, 4269. Most of these may be recognised in our
spectrum.
Second Spectrum. Yttrium Arc. — Powder metal in
carbon cup. Spectrum well defined, point lines absent,
notably those about H^ and ff and others generally
seen towards the violet. Yttrium and Erbium are
given as a combined spectrum by Dr. Watts, but our
photographed spectra have little in common.
Dr. Watts gives in our part of the spectrum, 4822 ;
then two we do not find ; and then 4674, 4643, 4505,
4422, 4397, 4374, 4357, 4309, 4236, 4227, 4176,
4167, 4142,4127,4102. 4102 is very well marked,
and if the Scale be adjusted to this line, many of the
others may be picked out.
Third Spectrum. Brass Arc, — Two pieces of
stout brass wire. Arc did not form well. A mixed
spectrum of Zinc and Copper, the principal lines of each
metal being easily distinguished, the zinc lines towards
the red end of the spectrum, the copper towards the
violet end.
Fourth Spectrum. Brass Spark. — Two points of
brass wire as electrodes. Spark passed freely, spectrum
deficient towards the violet, introduced to show the
double zinc line about 4925.
£ 2
52 PHOTOGRAPHED SPECTRA.
PLATE XX.
FiKST Spectrum. Zinc Arc, — Small piece of the
metal in carbon cup. Arc brilliant. Much oxide
formed. Lecoq de Boisbaudran gives [Plate XX.,
Chlorure de Zinc en solution] three brilliant Hues 4812,
4721, 4681, and another not so strong at 4630. Dr.
Watts gives (Huggins') faint lines at 5049 and 4970,
two strong ones at 4924 and 4911, a faint one at 4867,
and then three strong ones at 4809, 4722, 4679,
(Boisbaudran 's 4812, 4721, and 4681). Compare the
arc spectrum, the two tin and zinc spark spectra
on Plate XVIII. and the brass spark spectrum on
Plate XIX.
Boisbaudran's 4812, 4721, 4681, and 4630, are all
very prominent in the arc spectrum, together with a
double one at the other end of the spectrum, about
4060, (sed quaere a point line. It or a line very
approximate occurs in other arc spectra). In the tin
and zinc spark spectrum No. 1, 5049, 4924, and 4911,
and 4809, 4722, and 4681 are seen without 4630.
In tin and zinc spark No. 2 the three stronger lines
alone are "seen, while in brass spark 4924 and 4911
alone appear.
Such effects are probably due in the case of a single
metal to difference in strength, and temperature of
spark or arc ; but in the case of mixed metals the effects
produced, and the causes leading to them, seem to have
a complication of their own.
DESCRIPTION OF PLATES. 53
Second Spectrum. Zirconium Arc. — Thin flakes
of the metal in carbon cup. Arc short and brilliant,
thick coat of oxide formed, occasionally stopping the
current and requiring pole to be cleaned ; slit fine.
Spectrum characterised by three prominent shaded
sets of bands or lines towards the red end. Dr. Watts
gives (Thalen) five strong lines (intensity 10) at 4815,
4771, 4738, 4709, 4686, then follow (intensity 4)
4497, 4494, 4443, 4380, 4370, 4360, 4242, 4241,
4228, 4210, 4209, and lastly (intensity 8) 4155, 4149.
The five strong lines 4815 to 4686 are easily dis-
tinguished in our spectrum; and 4155, 4149, may be
picked out in the brighter part of the spectrum. There
also appear metal lines beyond ; until, at the extreme
violet end of the spectrum; we find two intense hnes,
one midway between H^ and H*^, and the other a little
beyond H^.
Third Spectrum. Zirconium and Palladium
Spark. — Small pieces of the metal in clips. Many in-
dications of sharp metal lines on the upper (Zirconium)
margin of spectrum about 4686, 4575, 4550, 4540,
4530, 4380, 4370, 4228, and 4155, (the last two
rather strong), and in other places. A line (two are
seen in the original plate), appears also in this and the
next spectrum at the extremity of the violet end, which
probably corresponds with the intense one in the arc.
Palladium margin weak, and lines not easily distin-
guished.
Fourth Spectrum. Zirconium Spark. — Small
flakes of the metal in the clips. Spectrum confined to
54 PHOTOGRAPHED SPECTRA.
centre, dark strong lines corresponding to 4228, and
4155 in last spectrum well seen. Three lines (Iron ?)
project from the upper margin of last spectrum in the
region about G, which may be also identified in this
spectrum. Note also line at extreme violet end.
PLATE XXI.
Scale and Solar Spectrum. — ^Both have been
previously referred to and described.
N.B. Potassium and Sodium were tried in arc and
spark, but caught fire and would not last long enough
to give an image. Caesium alum was tried (moistened
in glass cup) with spark, but gave no result. Silicon
in arc, the upper pole was quickly covered with a white
crust of oxide which stopped the arc current. Tan-
talum in arc gave only point hues.
THE GASES.
Some of the gases have been added by way of
supplement to the arc and spark spectra. The set
of the gas photographs is by no means complete ; and
they are rather experimental than otherwise, as three
different instruments have been used for their pro-
duction, arid the one which gave the best results came
last in the field. The spectroscopes employed have been
already described in the Introduction ; and are there
and in the following notes distinguished respectively as
A, B and C. As the dispersion (to preserve light) was
DESCEIPTION OF PLATES. 55
necevSsarily small, and as the gases give each a whole
and complete spectrum due to itself, it has not been
considered necessary to adapt a scale to the photographs.
Some of the gases are compared, the one with the
other ; and . others are compared with hydrogen, or
show one or more of the hydrogen lines : and in this
way a general idea is in most cases obtained of the
position of the principal lines or bands in the spectrum
without reference to scale. Of course individual aspect
is still more marked in tlie case of the gas spectra than
in the more complicated spark and arc spectra of the
metals. The remarks appended to the gas spectra will
mainly consist of notes as to the behaviour of the tubes
and brief indications of any special features in the
spectrum.
PLATE XXII.
NITROGEN.
First Print. Line Spectrum of Nitrogen.
Third Print. Band Spectrum of Nitrogen,
Centre Print. Line and Band Spectra of
Nitrogen compared.
The first photograph (line only) was taken with
spectroscope A. The centre and third with spectroscope
C. Two nitrogen tubes were employed, the one with
coarse capillary part for the line spectra, the other with
fine capillary for the band spectra.
The spectra were easily taken with twelve to fifteen
minutes exposure, and the small coil was generally
enough to work a single tube. To procure tlie line
56 niOTOGRAPHED SPECTRA.
spectra, the condenser (with two plates only) was in-
troduced into the circuit. The nitrogen line first spec-
trum is remarkable for its brightness towards the red
end, but with a falHng ofi* in light towards the violet.
This feature seems characteristic of the line spectra in
general. The line spectrum in the centre print is weak
and poor in lines as compared with the first hne
spectrum, partly perhaps for want of illumination in the
tube, but mainly that being the side tube, (the band tube
was in front of the slit) the image was weakened by
reflection from the comparison prism used to obtain the
second spectrum.
A fine line is noticed on the extreme left of the
band spectrum (centre print), which is attributed to
F hydrogen, and serves to mark the position of the
nitrogen bands. Twenty of these are counted in the
lower band spectrum.
PLATE XXm.
NITROGEN (continued).
First Print. Nitrogen Line and Band Spectra
compared.
Second Print. Nitrogen Band.
Third Print. Nitrogen Band and Hydrogen com-
pared.
Fourth Print. Nitrogen Capillary part of Tube
and Nitrogen Bulb part of Tube^ (near red pole, as dis-
tinguished from violet pole on next plate), compared.
All these were taken with the spectroscope B
(quartz), and are on the smaller scale. In the nitrogen
DESCRIPTION OF PLATES. 57
line and band compared spectrum, the band tube was
in front of the slit and the line tube at the side. In the
hydrogen and nitrogen compared spectra the hydrogen
tube was in front, and the nitrogen at the side ; and
unless the contrary is stated, it holds good throughout
as to all the compared spectra, that the tube at the side
is the upper spectrum and the tube in front of the slit
is the lower spectrum in the resulting plate.
As might be expected, the spectral images in the case
of the quartz spectroscope lose somewhat towards the
red end of the spectrum, but gain much in the direction
of the violet. About as many of the nitrogen bands
are counted as in the last plate, but they are not the
same. They commence at the bright edge of the band
spectrum in centre print of last plate, and extend con-
siderably further into the violet. An examination of
hydrogen and nitrogen compared spectra (third print)
will illustrate this. The faint line to the extreme left is
F hydrogen. The bright Une meeting the edge of the
upper spectrum is near-G, the next is A, and then two
other fainter lines of hydrogen.
PLATE XXIV.
NITROGEN (continued).
First Print. Nitrogen Band {Capillary) compared
with Nitrogen Violet Pole. Spectroscope C.
Second Print. Same, but reversed in position.
Spectroscope B.
Third Print. Violet Pole, — Spectroscope B.
In the first (large) print the nitrogen capillary
58
PHOTOGRAPHED SPECTRA.
bands, probably from the tube not being well adjusted
in front of the comparison prism, appear like lines.
This is, however, not without advantage, as they thus
indicate more clearly their position in regard to the
violet pole hues and bands. F hydrogen may be seen
as a faint line to the left of the violet pole spectrum in
this print. The following wave lengths, as given by
Dr. Vogel, may be interesting for comparison : —
»
»
Capillary part of Tube.
5066 bright.
4975
4913
4862 very faint.
4811 bright.
4721 „
4666 faint.
4644 bright.
4570 very bright.
4487 bright.
4417
4363
4357
4345
4273
99
9>
99
»
»
Violet Pole.
6147 feint.
5002 bright.
4912
»
4808 very faint.
4704 very intense.
4646 very faint.
4569 bright.
4486 „
4417 very faint.
4346 bright.
4273 very bright.
Our lines extend considerably more into the violet.
The violet pole has attracted considerable attention in
connection with the Spectrum of the Aurora, mainly o
o
account of the late Prof. Angstrom's opinion, that ' the
' feeble bands of the Aurora spectrum belong to the spec-
' trum of the negative pole, possibly changed more or
' less by additions from the banded or the line air
' spectrum.'
DESCRIPTION OF PLATES. 59
I have discussed tliis question at length in a paper,
on the Aurora Spectrum, published in the ' Philoso-
phical Magazine' for April 1875 ; and I only refer to
it now to point out that the difficulty of actual line
comparison which then existed might perhaps now
be conquered.
With one or other of the instruments we have used,
there really seems no reason why a photographic
image of the more refrangible rays of the Aurora Spec-
trum should not be obtained without difficulty. I saw
at Kyle Akin in Skye in September 1874, a fine double
arc Aurora of great brilliancy which lighted up the
whole landscape, and strongly impressed me with the
idea that if proper apparatus had been at hand some-
thing in that direction might have been accomplished.
Auroras have unfortunately been quite quiescent lately.
Should this state of things alter, the experiment would
be well worth trying. As much as possible, say two
thirds, of a long slit should be given to the Aurora, and
the remaining one third kept in reserve for a com-
parison spectrum. Dry plates might be used and a
considerable amount of exposure given. The Camera
should be directly pointed to the brightest part of the
Aurora. After exposure and before disturbing the
apparatus, the two thirds of the slit used for the Aurora
should be covered, and the remaining third which was
covered during exposure should be employed for the
projection of a tube or solar spectrum on the same
plate.
If a tube spectrum only were desired for comparison,
60 PHOTOGRAPHED SPECTRA.
a prism might be used on the slit in the usual way, but
I prefer a direct image when practicable.
To obtain absolute measurements of the lines a
double slit (the upper half moveable by a micrometer
screw) like one I have deposited at South Kensington,
might be employed. Two photographic images being
taken, one under the other, the lines are measured by the
relative position of the same lines in the two images
being compared with the ascertained value of the micro-
meter movement.
PLATE XXV.
NITROGEN (continued).
First Print. Band Spectrum of Nitrogen {Capillary)
with Magnet.
Second Print. Band Spectrum of Nitrogen
{Capillary) without Magnet
The Electro-magnetic experiments leading to these
plates have been fully detailed in the Introduction :
Spectroscope B (quartz) was used for them. The
plate with magnet is brighter, especially towards the
violet.
Centre Print. Ammonia {NH^ Tube, capillary
part fine, tube lighted up easily. A nitrogen spectrum
is alone prominent.
Fourth Print. Line Spectrum of Nitrogen lube, and
Spark in Air compared. — This print is from the original
without enlargement, and does not show so much as
the plate. The line tube spectrum was obtained by
use of the Condenser in the usual manner. The spark
DESCRIPTION OF TLATES. 61
passed between two platinum points introduced into
the circuit. The stronger hues correspond in posi-
tion.
Fifth Print, is introduced into the plate in con-
nection with the second spectrum (Spark in Coal Gas) on
Plate XXVII.
The upper spectrum is that of spark in air as taken
between Platinum points. The lower is spark in coal
gas (after referred to) and the combined spectra are
printed to illustrate the approximate position of the
hues in the spectrum of spark in coal gas at ordinary-
pressure as compared with spark in air. Spectroscope
C was used. Image not very good, but better on plate
than in the print. It would not bear enlargement with
any advantage.
PLATE XXVI.
HYDROGEN.
First Print. Hydrogen Tube, — Small in capillary-
part, lighted up well with small coil. A portion of
the capillary bore, comprising the whole circumference
of the tube is decomposed, and has the appearance of
being obscured by a yellow white coating. The
bright red tint of the discharge was lost here, and
the lines of the spectrum were partly extinguished
in a white misty haze. This effect is seen in the
print.
The spectrum, as to principal hues, will be seen to
consist of —
62 rilOTOGRAPIlED SPECTRA.
No. 1. F. 4861.
2. Near-G, 4340 (G 4307).
3. A 4101.
4. A sharp bright line, not quite as distant
from h as h is from G.
5. A line faintly seen in the print beyond
No. 4, not quite as distant from No. 4, as
No. 4 js from h.
No. 5, in the original plate, is fairly strong, and
close to, and on each side of it, are also seen two single
fine lines, the one on the violet side being rather the
more distant (see also Centre Print, Plate XXVIII.).
Lines of some breadth and intensity are to be
remarked between the more prominent lines before
described. Two short ones between No. 1 and No. 2
(five are counted on the plate), three or more between
No. 2 and No. 3, and three between No. 4 and No. 5.
The spectrum is also filled with a number of very
fine and sharp lines, traces of which are indicated in
the print. Whether these intermediate lines are due
to hydrogen or to tube impurity is not clear ; but as
some of the coarser ones are traced in the second
spectrum on next plate, (Spark in Coal Gas), it is
probable that these at least are due to the gas.
Second Print. Spark in Coal Gas. — ^This spectrum
and the way it was obtained have been already
described in connection with the Carbon Spectra.
Another but less bright print is found on Plate VL
This spectrum is on the same scale as the arc
and spark spectra, and therefore larger than our Gas
DESCRIPTION OF PLATES. 63
spectra in general. Tlie original, before enlargement
is found on Plate XXXIII. The print is liere intro-
duced to illustrate the expansion of a hydrogen line.
Note traces of a narrow dark space dividing the centre
of the expanded line. The sharp hues are attributed
to Carbon.
Third Print. Hydrogen Tube^ taken with spectro-
scope B, wide sht. Lines 1, 2, 3, 4, and 5, in last
spectrum are brightly seen, (No. 5 very bright), a sixth
is easily traced some distance beyond, and a seventh
faintly indicated where the continuous spectrum ends.
PLATE XXVII.
HYDROGEN (continued).
First Print, Compared spectrum. Spark in Air
between Platinum Points^ and Hydi^ogen Tube, — Spectro-
scope C. Large coil and condenser used for spark.
Small coil for the tube. Exposure for tube 15 minutes,
for spark 5.
The spark spectrum is seen to extend far into the
violet ; considerably beyond the spark in air, as taken
in combination with the metals. The four principal
hydrogen lines, commencing with F, are well seen,
some intermediate ones faintly.
Near-G is the only hydrogen line that can be
absolutely traced into and through the air spectrum.
Second Print. Spark in Coal Gas at ordinary
pressure, — The manner in which this spectrum was
obtained has been described under tlie head of Carbon
64 PHOTOGRAPHED SPECTRA.
among the Arc and Spark Spectra, and the peculiar
difference between this and the print, on Plate XXVI.
(also spark in Coal Gas) has been noticed.
This spectrum should be compared with the first
print in this plate, (Spark and Hydrogen) arid
with hydrogen on the last plate. TKe image is en-
larged very slightly more than the other two spectra,
but not enough to prevent easy comparison. Taking
the principal lines of Hydrogen in their order, —
F is seen as a bold very bright expanded line.
Near-G is seen to the left of a well defined line
not found in the ordinary hydrogen spectrum, as a
still more expanded bright band or stripe with conical
ends. A bright sharp line between F and near-G,
surrounded by a nebulous halo coincides with one of
two short lines in the hydrogen tube.
Beyond near-G, we have a blaze of continuous
spectrum, crossed by four prominent lines.
The first of these lines has been already noticed,
and does not appear in the hydrogen spectrum.
The second falls very close upon the place of h
in the hydrogen tube.
The third does not appear in the hydrogen tube.
The fourth, and last, and the most expanded, falls
close upon the place of No. 5 in the hydrogen spectrum.
Intermediate of Nos. 1 and 2, and of Nos. 2 and 3,
are faintly but distinctly traced some of the less strong
lines of the hydrogen tube. The general position of
this spectrum as compared with air is indicated by the
small print on Plate XXV. before described.
DESCRUmON OF PLATES. 65
PLATE XXVIII.
OXYGEN.
First Print. Band Spectrum of Oxygen^ tube
No. 1^ spectroscope C.
Second Print. Band Spectrum of Oxygen^ tube
No. 2, same spectroscope.
These two tubes were worked by the larger coil,
with batteries purposely weak; exposure fifteen
minutes. In the case of No. 1 tube the colour of the
capillary stream was a pale pink. There was consi-
derable stratification in tlie bulbs of both tubes.
The spectrum of No, 1 is a short bright one, com-
posed of a mixture of oxygen and hydrogen lines, the
latter probably due to moisture in the tube. F hydro-
gen is seen as a single line to the extreme left;
near-G is seen very bright at the edge of the illuminated
part of the spectrum, h is seen in the centre of the
spectrum, apparently doubled by a strong oxygen line.
The other less distinct lines or bands are those of
oxygen. In the plate some finer lines are seen inter-
mediate of the coarser ones. Professor Draper is said
to have recently found some of the oxygen Unes as
bright ones in the solar spectrum.
The capillary stream of tube No. 2 was somewhat
redder in tint. The spectrum was taken and enlarged
as one of oxygen, to accompany that of No. 1 ; but a
comparison with the upper print on Plate XXVI. will
show that while the continuous spectrum and some
p
66 PHOTOGRAPHED SPECTRA.
indistinct lines or bands are probably due to oxygen,
the principal bright lines are those of hydrogen. It
will be noticed, too, that the triple line mentioned as .
No. 5 and feintly seen in the hydrogen spectrum, shows
in the spectrum now examining (to the extreme right)
as a strong double line, with shading off towards the
violet.
Third Spectrum. Line Spectrum of Oxygen. —
This was obtained in the usual way, by introduction of
the Condenser (with two plates) into the circuit. The
spectroscope used was A.
Four line spectra are printed which have been
taken with this instrument : Nitrogen, Plate XXTI. ;
the present (Oxygen) ; Carbonic Acid, Plate XXX. ;
and Coal Gas, Plate XXXIII. Each of the three last
spectra, though differing in other respects, has a marked
character in common, viz, a bright line to the left,
as jumed to be F hydrogen, and a bright broad band of
light more towards the centre with a sharp line close
adjoining on the violet side. The other lines by their
variation show that the spectra, as a whole, are not
by any means identical; but these particulars seem
constant. It might be expected that the bright line
adjoining the band would be ' near~G ' hydrogen, but
this is not the case. An examination of the original
plates shows that the enlargements are strictly correct,
and that the broad band itself exactly occupies the
place of ' near-G ' in the hydrogen spectrum. It would
seem that the images of spectroscope A give the line
spectrum towards the red end, while those of spectro
DESCRIPTION OF PLATES. 67
scope B (quartz) give the line spectrum towards tlie
violet (see Plate XXTX. line oxygen).
PLATE XXIX.
OXYGEN (continued).
All the photographs on this plate were taken with
spectroscope B (quartz).
First Print. Band Spectrum of Oxygen^ tube No. 1.
— This spectrum extends, in an even series of bands,
considerably into the violet. In the spectrum of
oxygen on last plate, we count only six principal coarse
lines or bands. In this print we count no less than
fifteen. Probably from some difference in lighting up
of the tube, one hydrogen line only shows in this
spectrum, and the bright oxygen line doubling the
hydrogen line in the spectrum on last plate though
present is not nearly so conspicuous.
Print No. 2. Water Gas.—T\ibG marked HgO,
worked as above, colour of capillary red, but not so
red as hydrogen. The principal lines of the latter are
well distinguished. The oxygen spectrum is not so
bright, especially towards the violet as in the last print.
Third Print. Band Spectra of Oxygen and Ni-
trogen compared. — Nitrogen tube and spectrum much
the brightest. Oxygen spectrum towards red a com-
paratively even set of bands. Nitrogen, in sets of
bands.
Fourth Print^ Line and Band Spectra of Oxygen
F 2
68 PHOTOGRAPHED SPECTRA.
compared. — Line tube the brightest. Line spectrum
very bright towards the red, but obscured towards the
violet.
PLATE XXX.
CARBONIC ACID.
First Spectrum. Band Spectrum of Carbonic Add.
— Spectroscope C. Tube marked C A of rather large
bore, worked by large coil, much stratification extending
even through the capillary, stream of capillary light,
bright and of silvery grey green tint. Spectrum much
filled up by obscure sets of bands or lines, except in the
positions occupied by a bright line in the centre and a
dark space more towards the violet. F hydrogen shows
to tlie extreme left. The other hydrogen lines are not
seen. Note sharp bright line separated from main
body of the spectrum towards the red.
Second Print. Spectroscope C. — This was a tube
marked SO3. The light was pearly white. The
spectrum turned out to be carbonic acid, probably
from some impurity in the tube. See also second and
third prints on Plate XXXV. The tube was worked
by the large coil and two weak bichromates.
Third Print. Line Spectrum of Carbonic Acid.
— Spectroscope A. Condenser in circuit. Tube filled
with stream of white light. Compare line spectra of
oxygen and of coal gas taken with same instrument.
DESCRIPTION OF PLATES. 69
PLATE XXXI.
CARBONIC ACID (continued).
First Print. Spectral image, taken with spectro-
scope A, of capillary part of carbonic acid tube (C A)
wide slit. Stratification well seen. Print from original
negative not enlarged.
The three remaining spectra on this plate were
taken with spectroscope B.
Second Print. Carbonic Acid Tube^ Band Spectrum,
— This spectrum \xa taken with the quartz instrument,
though the same, differs somewhat in actual appearance
from our print on last page. The two left-hand single
lines are absent. The left-hand edge of the centre
part of the spectrum is comparatively brighter. The
bright band and dark interval before referred to are
still more strongly defined.
Beyond the bright band and next to the dark inter-
val which nearly ends the spectrum on the last plate,
we get in our present spectrum a set of six lines or
bands, the first only of which is faintly indicated in the
spectrum taken with instrument C.
Thjrd Print. Line Spectrum of Carbonic Acid
compared with Line Spectrum of Oxygen.
Fourth Print. Band Spectrum of Carbonic Acid
compared with Band Spectrum of Oxygen.
Some years ago Mr. Henry K. Procter and myself
were much struck with the closeness in position of the
three prominent briglit lines or bands in the yellow,
70 PHOTOGRAPHED SPECTRA,
green, green and blue, in hydrocarbon tubes as compared
with like lines in an oxygen tube. The three lines
were so nearly identical in position in the compared
tubes that a fine pointer and high power eyepiece
failed to distinguish apart their sharper margins. But
for a certain want of accord in tint and intensity of the
two spectra, we began to suspect the identity of the
oxygen spectrum, and Mr. Procter even conjectured
that oxygen might have only a continuous spectrum,
and that the bright lines might arise from carbon
impurity in the tubes.
Our compared photographic spectra lie much more
towards the violet end of the spectrum (beginning with
the more refrangible of the three lines or bands above
referred to), but it is pretty clear from an examination
of them that, in this part of the spectrum at least, the
spectra differ considerably. The line spectra approach
the nearest in position, but there is a marked and
distinct character to each of these. The band spectra
are widely different. The smooth and even character
of the band spectrum of oxygen contrasts strongly
with the sharper and more defined lines and bands of
the carbon spectrum. Some few lines only towards
the violet of carbonic acid appear to correspond with
bands in the oxygen spectrum. The one extremely
bright line or band in carbonic acid is conspicuous
for its absence as such in oxygen.
DESCIUPTION OF PLATES. 71
TLATE XXXII.
COAL GAS.
First Print. Band Spectrum of Coal Gas. — Spec-
troscope C. Stream in tube whiter and brighter
than carbonic acid, much stratification, exposure 15
minutes. Spectrum as reading from the red composed
of foiu: faint single hues followed by an evenly lighted
broad continuous portion, crossed by many well-defined
briglit lines or narrow bands.
This continuous portion terminates with a most bril-
liant band or set of lines shading ofi* towards the violet,
which is immediately succeeded by a fairly strong and
then a faint Une as the last indication of the spectrum.
Compared with the Hydrogen spectrum, F is
seen faintly to the extreme left, foUow^ed by the two
short Unes seen in the Hydrogen spectrum between F
and near-G. Next comes an outstanding sharp line,
also seen in the Carbonic Acid spectrum.
Near-G Hydrogen is next seen as a well-defined
line on the edge of tlie conthiuous portion. The
very bright line exactly in the centre of the print does not
fall in the place of h but of a line a little beyond A, also
seen in the Hydrogen spectrum. The spectrum forms
a fine photograph, and nearly all that is seen in the
plate is got out in the print.
Second Print. Cyanogen, — Tube lent to me by
Mr. W. G. Lettsom, lighted up easily with a white
glow, fines and bands sharper and more separated by
72 PHOTOGRAPHED SPECTRA.
dark intervals than in the Coal Gas spectrum. As-
suming the first (single) line on the left to be near-O
Hydrogen, a few lines in the spectra of coal gas and
cyanogen fairly correspond, and the general character
of the two spectra is somewhat alike. They, however,
differ in detail.
Third Print. Coal Gas Tube. — Spectroscope B.
The general aspect of the spectrum is that of the first
print, except that the lines are not so well defined, but
blend into bands.
The especially bright band towards the violet is
easily recognised, and beyond it extend three bright
bands not seen in the large spectrum.
PLATE
COAL (?ul/Sf (continued).
First Print. Line Spectrum of Coal Gas. — Con-
denser in circuit, exposure 20 minutes. Note former
remarks on line spectra of oxygen and carbonic
acid.
Second Print. Line and Band Spectra of Coal Gas
compared. — ^The line spectrum commences with the
band and bright hue so conspicuous in the first print,
and then succeed two other bright lines or bands, with
fine lines between. The last band towards the violet
in the line spectrum corresponds with the very bright
band in the band spectrum.
Third Print. Coal Gas Band Spectrum compared
DESCRIPTION OF PLATES. 73
with Hydrogen Lines, — Spectroscope A. Print from the
original negative, not enlarged; near-G is seen on the
edge of the first bright band or set of lines in coal
gas.
Fourth Print. Spark in Coal Gas at ordinary
pressure. — Same spectroscope as used for Arc and Spark
Spectra. Print from original negative, v^hich was after-
wards enlarged to form prints on Plates VI. and
XXVI.
PLATE XXXIV.
OTHER HYDROCARBONS.
First Print. Olejiant Gas. — Tube fairly bright.
Spectroscope A. A broad bright band, (probably a set
of lines or bands), and a nebulous bright line beyond,
towards the violet, are very marked in this spectrum.
As these are only feebly indicated in the other two
spectra of this gas, they may probably have depended
upon the lighting up of the tube.
Second Print. Olejiant Gas. — Spectroscope C.
Spectrum Avith w^ell-defined lines. The faint one
towards the extreme left seems to be one of the lines in
Hydrogen intermediate of F and near-G. As in the
case of coal gas, near-G is on the margin of the con-
tinuous part of the spectrum, while the fifth bright line
in the spectrum falls upon the place of the line in
Hydrogen just beyond h.
The bright broad band in the first print is indicated
by a few faint lines.
74 PHOTOGRAPHED SPECTRA.
Third Print. Olejiant Gas, — Spectroscope B.
The set of two double and two single bright lines in the
last spectrum is easily recognised on a smaller scale.
Three other bright bands are seen towards the violet.
Fourth Print. Turpentine Vapour, — Tube not
bright, large coil used. Exposure fifteen minutes.
As might be expected, the print bears a likeness to the
Olefiant spectrum.
Fifth Spectrum. Ether Vapour, — Spectroscope C^
tube difficult to light up. What is seen of spectrum
resembles Olefiant and Turpentine spectra.
PLATE XXXV.
SULPHUR.
First Print. Sulphur. — A short German tube,
with small bulbs and a bent capillary part. The bulbs
contained a small quantity 'of solid sulphur. The tube
was suspended, and the lower bulb heated by a spirit-
lamp. When the sulphur was partly melted, one half
of the capillary was white in colour and the other half
red. As the heat was gradually applied the spectrum
of sulphur of first order was seen to spread up the tube
as a set of bright bands, which by management of the
lamp could be kept at a definite height. The spectrum
independent of the sulphur vapour was found to be
hydrogen, with the principal lines very bright. Photo-
graphs were first tried with A and B spectroscopes, but
were not satisfactory. Several plates were subsequently
DESCRIPTION OF PLATES. 75
taken with spectroscope C. We tried to take tlie spec-
trum lower lialf sulphur and upper half hydrogen, but
failed, probably for want of proper adjustment of the
lamp. In each case we found only the sulphur spec-
trum on the plate. The plates were all much alike, and
only differed in distinctness of the bands.
Second Print. Another print of SO3 Tube Spec-
trum. — Spectroscope C, see Plate XXX., where by con-
parison the spectrum is seen to be a carbonic acid one,
arising we presume from impurity in the tube.
Third Print. SO^^ Tube. — Spectroscope B, same
result as above. Compare with carbonic acid spectra,
Plate XXXI. The slit must have been a little wider,
or the tube less bright in this instance, as the spectrum
is more continuous and the lines not so sharp.
PLATE XXXVI.
First Print. Silicic Fluoride Spectrum. — Tube
easily worked, capillary a beautiful violet, bulbs golden
brown. Under mfiuence of large electro-magnet, stream
of light became less violet and more red in tint, con-
tracted itself, and ran through the bulbs from pole to
pole. At the same time a slight noise, between a
whistling and a metallic ring of high pitch, was heard.
The stream was curved in the bulbs towards one
side or the other as the current was reversed. Good
photograph, lines some twenty- four in number, sharp,
and well separated. A fine shaded group commences
the spectrum towards the red end. This group in
76 PHOTOGRAPHED SPECTRA.
the spectroscope is of a brilliant violet tint, and at once
identifies the spectrum.
Second Print. Silicic Fluoride Spectrum, — Spec-
troscope B. The spectrum does not seem more ex-
tended into the violet in this instance, but a band or
set of lines towards the centre is brightened up. A
second photograph was taken with the tube under the
influence of the electro-magnet, same time of exposure.
The image was identical, but very decidedly fainter.
Third Print. Tin Chloride. — Spectroscope B. This
tube was very difficult to photograph. The small coil
only did not sufficiently light the tube, the large coil
was too much for it. The discharge was in the form
of a slender bright green thread running through the
tube. Forashorttime all went well, after that the stream
intermitted and almost broke up, and flashes of light
only took its place. At the same time the metal lines
grew fainter in the spectrum, and the bulbs of the tube
were filled with a yellowish flare. These, on subsequent
examination, were found covered with a whitish crust.
Only one fair plate was obtained, of which a print is
given. Some fine metallic looking lines seen in the
spectrum do not come out in the photograph.
Fourth Print. Iodine Tube. — ^This was lighted by
the small coil only. The photograph shows two sets of
bands, each gradually degrading towards the violet, with
a dark interval between them.
Many fine lines seen in the tube spectrum do not
appear in the photograph.
Fifth Print. Spark in Iodine Vapour. — A bulb
DESCRIPTION OF PLATES. 77
similar to that employed for spark in coal gas was used.
The ends were lightly plugged with cork and the iodine
vapourised by a spirit-lamp.
When the vapour filled the bulb, the spark spectrum
as seen through it with a small direct vision spectro-
scope showed marked absorption bands.
Traces of these (better on the plate than in the
print) may be found on the photograph.
A Chlorine Tube^ it has been mentioned, baffled us.
We tried it with the small coil, and exposure gave no
image apparently for want of brightness. We then
tried it with the larger coil. At first the tube shone
with a yellowish green stream running from pole to
pole, the bulbs being filled with a somewhat dull purple
glow. Almost suddenly one pole and then the other
changed to a brighter and whiter purple. One pole
then changed to a rich salmon colour, the opposite
pole remaining white surrounded by a purple glow.
Current reversed, and both bulbs then became salmon
colour, with considerable stratification. Ultimately the
capillary became a pinkish white, one pole a red buff
and the other a bright lilac. The yellow green line
was then altogether lost.
On reversing current, the poles changed. The
spectrum when the plate was examined was found to
be nitrogen.
J
^ I.
'i
/'
..^/
notp: to oxygen 8PECTRUM.
Since the foregoing has been penned, Professor Draper's in-
teresting paper and photograph have been made public.
The solar spectrum from about 4350 to 3900 is photo-
graphically compared with the lines of oxygen, as seen in
spark in air, and coincidences are sliown, principally at the
double lines 4319 4317, 4190 4184, and tlie triple line
4076 4072 4069. The air spark spectrum in Professor
Draper's photograph, making allowance that it is on a scale
of three times the size, and that it has less of continuous
spectrum filling up between the lines, very closely resembles
our air spectrum fine slit Plate I. Most of the lines
in each are easily compared and identified. The three
principal nitrogen lines are recognised, the one near 4000
by its strength and brightness, and the other two by
their fuzzy expanded character : the oxygen lines by their
comparative sharpness. In our solar spectrum, we find
faint traces of the bright lines which are alluded to by
Professor Draper, and their character suggested. It is
curious that these bright lines in the solar spectrum should
have been so long overlooked, or not more closely examined ;
for in the spectrum taken from an illuminated cloud
with a large direct vision spectroscope their existence is
readily detected. Doubtless they have been generally re-
garded as spaces or effect of contrast between the dark lines,
and it is indeed only after a certain amount of study whether
of the spectrum or of a photograph, that they appear to
stand forward from among the dark lines in an independent
character. Judging from his paper, Professor Draper seems
to have found with his incompara))ly larger and more perfect
80
PHOTOGRAPHED SPECTRA.
apparatus, the same sort of diEBeulty in the tube work that
we experienced in ours on a smaller scale. Professor Draper
makes the remark, ' I do not think that in comparisons of
the spectra of the elements and smi, enough stress has been
laid on the general appearo/nce of Imea apart from tkevr mere
position ; in photographic representatioDs this point is very
prominent.'
Our set of Plates amply illustrates the justice of this
remark of the Professor's,
INDEX TO ARC AND SPAllK SPECTRA.
Air wide Slit .
Air fine Slit .
Arsenic Spark
Aluminium Spark .
Aluminium Arc
Antimony Spark
Antimony Arc
Bismuth Spark
Bismuth and Nickel Spark
Bismuth and Tellurium Spark
Bismuth Arc .
Barium Spark
Beryllium (Iron) Arc
Boron Arc
Calcium (Zinc) Spark
Cadmium Spark
Cadmium Arc . .
Carbon Points
Carhon Points ruled out
Coal Gas Spark in .
Chromiaim Arc
Cohalt Arc .
Copper Spark .
Copper Arc .
Copper and Silver Arc
Copper, Gold, and Silver (Alloy) Arc
Copper and Iron Spark
Didymium Arc
Erhiaim Arc .
Gold Arc
Indium Arc .
Indium Spark
II
PIATB
PA OB
I.
18
I.
18
I.
18
iU
/. XVII. 19,
40,47
II.
19
II. X.
19, .34
II.
19
III.
20
III.
20
III.
20
ITT.
21
IV.
21
IV.
22
IV.
22
IV,
23
V.
23
V.
23
V.
23
V.
24
VI.
24
VI.
26
VI.
27
VI.
27
vn.
27
XV.
43
VII.
27
VITT. IX.
31
VTT.
28
VII.
29
VIII.
30
VIII. .
30
XVI.
45
82 INDEX.
PLaTR pagb
Iridium Arc ........ Vin. 30
Iron and Copper Spark VIII. 31
Iron and Copper Spark IX. 31
Iron Arc IX. 31
Iron Arc " . . IX. 31
Iron and Selenium Spark IX. 32
Iron Meteoric Arc ....*.. X. 33
Iron Meteorite Arc X. 33
Lead Arc X. 34
Lead and Antimony Spark X. 34
Lead and Magnesium Spark XI. 35
Magnesium and Lead Spark XI. 35
Magnesium Spark XI. 35
Magnesium Arc * XI. 35
Manganese Arc XII. 36
Manganese Arc XII. 36
Mercury Spark XII. 37
Molybdenum Arc XII. 37
Nickel Arc . Xm. 38
Nickel Spark in. 20
Niobium Arc . . XIII. 38
Palladium Arc XHI. 39
Palladium Spark XVH. XX. 47, 48, 53
Platinum Arc . . * XIII. 39
Rhodium Arc . XIV. 40
Rutbenium Arc XTV. 40
Scale L XXI. 17
Selenimn and Tellurium Spark .... XTV. 40
Selenium and Iron Spark IX. 32
Selenium and Aluminium Spark .... XTV. 40
Silver Spark XV. 42
SHverArc ....'.... XV. 42
Silver and Copper (Alloy) Arc .... XV. 43
Solar Spectrum XV. XXI. 43
Strontium Spark XVI. 44
Tellurium Spark . . . . .HI. XIV. XVI. 20, 40, 45
Thallium and Indium Spark XVI. 45
Thallium Arc. . . - XVI. 47
Titanium Spark . XVH. 47
Titanium, Aluminium, and Palladium Spark . . XVII. 47
Titanium Arc XVII. 47
Tin Arc XVIL 49
Tin and Zinc Spark XVIII. 49
Tin and Zinc Spark XVIII. 49
INDEX.
83
Uranium Arc .
Vanadium Arc
Wolfram Arc .
Yttrium Arc .
Zinc Alloy (Brass) Arc .
Zinc Alloy (Brass) Spark
Zinc and Tin Spark
Zinc Arc
Zirconium Arc
Zirconium and Palladium Spark
Zirconium Spark
PIATE
PAGE
XVIII.
60
XVIII.
50
XIX.
50
XIX.
51
XIX.
61
XIX.
51
XVIII.
49
XX.
62
XX.
63
XX.
63
XX.
63
INDEX TO THE GASES.
Ammonia ....
Carbonic Acid Band
Carbonic Acid Band [SO3]
line
Band Quartz .
Stratification .
Band and O, Band
Line and O. Line
Coal Gas Band
Band Quartz .
Line
Line and Band
Band and H
Spark in .
Spark in, and Spark
Cyanogen
Ether Vapour
Hydrogen Tube
in Coal Gas .
Quartz .
and Spark in Air
Lines in Coal Gas
Iodine Vapour
„ Spark in
Nitrogen Line
ft
if
ff
ff
in Air
ff
ff
ff
ff
XXV. 60
XXX. 68
XXX. 68
XXX. 68
. XXXI. 69
. XXXI. 69
. XXXI. 69
. XXXI. 69
. XXXII. 71
. XXXII. 72
. XXXIII. 72
. XXXIII. 72
. XXXIIL 72
XXVI. XXVII. XXXIII. 62, 72
XXV. 61
. XXXII. 71
. XXXIV. 74
. XXVI. 61
. XXVI. 62
. XXVI. 63
. XXVII. 63
. XXVII. 63
. XXXVI. 76
. XXXVI. 76
. XXII. 55
1
84 INDEX.
PLATE PACK
Nitrogen Line and Band XXII. 56
„ Band XXII. 65
„ Band Quartz XXIII. 56
„ Line and Baud , . . . . XXIII. 56
„ Capillary and Bulb XXIII. 56
„ Band and H XXIIL 56
„ Band (Capillaiy) and Violet Pole . . XXIV. 57
„ Violet Pole Quartz XXIV. 67
„ Violet Pole and Capillary . . . XXIV. 57
„ without Magnet XXV. 60
„ with Magnet . . . . . . XXV. 60
„ Line and Spark in Air .... XXV. 60
„ Spark in Air and Spark in Coal G^as . . XXV. 61
defiant XXXIV. 73
„ XXXIV. 73
„ Quartz XXXIV. 74
Oxygen Band, Tuhe No. 1 XXVIH. 65
„ „ Tube No. 2 . . . . , XXVin. 65
„ Line XXVin. 66
„ Band Quartz XXIX. 67
„ (Water Gas) . . . . . . XXIX. 67
„ Line and Band XXIX. 67
„ Band and Nitrogen Band .... XXIX. 67
SiHcic Fluoride XXXVI. 75
„ Quartz XXXVI. 76
Sulphur XXXV. 74
Sulphuric Acid [SOg] XXX. XXXV. 68,75
„ Quartz . XXXV. 75
Tin Chloride XXXVI. 76
Turpentine Vapour XXXIV. 74
LosDoy : rnixTBD ay
SrOTTISWOODB AND CO., NlEW-STaEBT SQrTABEB
AXD PAIlLiAMEXr STREET
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1
ARSENIC. SPARK.
n
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ALUMINIUM. SPARK.
ALUMINIUM. ARC.
Iliii^l
\NT \ MONY. SPARK.
ANTfMONV. ARC.
■E
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BISMUTH. SPARK
ISMUTH. SPARK.
i.jm
ilSMUTH. SPARK.
UiMMIi
TELLURIUM.
BISMUTH. ARC.
BARIUM. SPARK.
BERYLLIUM. (iROn) ARC.
» ■! ^
BORON. ARC.
:■
CALCIUM, (zinc) spark
ft.
S
^ ■
CADMIUM. SPARK
CADMI UM. Anc.
CARBON POINTS.
CARBON POINTS RULED OUT.
SPARK IN COAL GAS.
CHROMIUM. ARC,
COBALT. ARC
B
1
LiatikMiidllll
COPPER- SPARK
t
f • •
V.
V
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i.
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COPPER POINTS. ARC,
ERBIUM. ARC.
GOLD. ARC.
NDIUM. ARC.
IRIDIUM. ARC.
^^lllll^ll^
IRON. SPARK
f-
1':
RON. SPARK, (*Mi coptfr)
IRON, ARC.
IRON- ARC,
RON i SELENIUM. SPARK.
- /
J
IRON, METEORIC. ARC.
IRON, ME.TEORITE. ARC
LEAD. ARC.
^Jjjllljjj^^
LEAD. SPARK.
ANTl M ON
LEAD. SPARK.
i^AGNESIUM. SPARK,
.\kX\.\
MAGNESIUM. SPARK
MAGNESIUM.
MAGNEISI U M. ARC.
mangame.se. ARC-
MANGANESE, ARC.
MERCURY. SPARK..
•«W
MOUrBDEN U M, ARC.
NICKEL. ARC,
PALLADIUM. ARC.
PLATtNUM. ARC.
k#
RHODIUM. ARC.
RUTHENI UM , ARC.
iJH!
TELLURIUM.
nmm\
ALUMINIUM.
J
r-.
p/k^ior:
SILVEIR SPARK.
SILVER ARC.
ALLOY. SILVER &. COPPER. ARC.
SOLAR SPECTRUM.
' §
STRONTIUM. SPARK.
TELLURrUM. SPARK.
THALLI UM. SPAR
THALLIUM. ARC.
\
TITANIUM, SPARK.
4. ALU MINIUM. SPARK
ili'
TIN, AKC.
■EH
A»
TIN. SPARK.
U RAN I UM. ARC
VANADi UM. ARC.
A-OLrftAM ARC.
YTTRIUM, ARC.
SAME. SPARK.
^ ,*
■KH
ZIRCONIUM. ARC.
ZIRCONIUM. SPARK
fVW
ZIRCONIUM. SPARK.
SCALE
SOLAR SPECTRU M.
NITROGEN.
■
NITROGEN. J'/a^eXXSr.
N. LfNE QUARTZ. N.BAND QUARTZ.
N. BAND QUARTZ.
N. CAPILLARY QUARTZ.
NITROGEN. J'&UXW
N WITH MAGNET. N WITHOUT MAGNET.
AMMONIA- QUARTZ.
SPARK IN AIR.
SPARK IN AIR.
SPARK IN C.G.
HYDROGEN.
jv!iu xa7.
HYDROGEN.
SPARK tN AIR.
SPARK IN COAL GAS.
*'■<
OXYGEN.
BAND. TUBE N?
BAND. TUBE N92.
I I
OXYGEN.
BAND. QUARTZ.
WATER GAS. QUARTZ.
BAND. QUARTZ,
LINE QUARTZ.
CARBONIC ACID. J^&Oe JQQC.
S.03. (FOR COMPARISON.)
•i •
1
Y -
4
CARBONIC ACID.
C.Oi STRATIFICATION. C.Oi BAND. QUARTZ.
COAL GAS. J'&tfeXXXn
COAL GAS BAND.
CYANOGEN.
C.G.BAND. QUARTZ.
.1
COAL GAS.
C.G. LINE QUARTZ.
SPARK IN C.C.
OLEFIANT GAS. /'/afe XXXtV
Same quartz.
TURPENT
NE VAPOUR.
1
1
ETHER VAPOUR.
S.Oj. QUARTZ.
SILfCIC FLUORIDE. I'^le SOU.
I r
i
SAME. QUARTZ.
TIN CHLORIDE,- QUARTZ.
IODINE VAPOUR. QUARTZ
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